Saturday, August 6, 2016

Breeding Leach's Storm-Petrels in Southwest Nova Scotia

Leach's Storm-Petrels in Nova Scotia
Leach's Storm-Petrels are a species frequently seen by fisherman, but only seen by birders who put the effort in. While they do nest on many of our Atlantic Coast islands, they usually feed far offshore and only travel to and from their colonies at night (McLaren 2012). Going out to sea is the best way to see these birds, but you might catch a distant view of one from our headlands where they are only numerous during storm events. I observed a single individual in Yarmouth Harbour only a few hundred metres from the mainland on June 11, 2016, and two were seen at the same location a few days later by Ellis d'Entremont, so near shore sightings are a definite possibility but are rare.

Leach's Storm-Petrel at German Bank, August 29, 2015. Photo by Alix d'Entremont.

Bon Portage Island [43.469349, -65.751828] in Shelburne County is the most well known breeding site for Leach's Storm-Petrels in Nova Scotia, and is the largest in the Maritime Provinces (Stewart et al. 2015). An estimated 50,000 pairs (Oxley 1999) of these procellariiformes (tubenoses) spend the summer months on this island that is owned by Acadia University. The 3 km by 0.5 km mostly forested island, officially known as Outer Island on the maps, is internationally recognized as an Important Bird Area. Since fall of 1995, the Atlantic Bird Observatory monitors migration through mist netting.

During one of my first visits to Bon Portage, I met with Ingrid Pollet, a storm-petrel researcher. She has contributed to published studies such as Foraging movements of Leach's storm-petrels Oceanodroma leucorhoa during incubation where archival light loggers were used to show that the average foraging trips for adult Leach's Storm-Petrels on Bon Portage was 1303 km with an average trip time of about 5 to 6 days.

Banders' building on Bon Portage, September 2, 2012. Photo by Alix d'Entremont.

Weighing a Cape May Warbler on Bon Portage, September 2, 2012. Photo by Alix d'Entremont.

David Bell holding a Blackpoll Warbler with a radio transmitter on Bon Portage, August 23, 2014. Photo by Alix d'Entremont.

One of the field crew bunk houses on Bon Portage, September 2, 2012. Photo by Alix d'Entremont.

Ingrid Pollet reaching into a Leach's Storm-Petrel burrow for research on Bon Portage, July 21, 2013. Photo by Alix d'Entremont.

Ingrid Pollet holding an adult Leach's Storm-Petrel on Bon Portage, July 21, 2013. Photo by Alix d'Entremont

Ingrid Pollet holding a banded Leach's Storm-Petrel on Bon Portage, July 21, 2013. Photo by Alix d'Entremont.

The other important breeding site is a relatively smaller colony at Country Island, Guysborough County [45.101784, -61.542582]. This is a circular island at about 500 m in diameter with an estimated 8700 (Pollet et al. 2014a) to 12,000 (Env. Canada data) breeding pairs of Leach's Storm-Petrels.

While breeding popultion is difficult to monitor due to the remoteness of the colonies, the bird's nocturnal behaviour and its hidden burrow entrances, observations at Bon Portage and Country Island suggest that the population is stable or has declined slightly between the 1st and 2nd Maritime Breeding Bird Atlas. (Stewart et al. 2015)

The map below shows that Leach's Storm-Petrels are absent in the Bay of Fundy and the Northumberland Strait areas. This is due to their preference for the cooler Atlantic Coast waters and their requirement for predator free islands, which are much more common on our province's southern coast. Interestingly, Tufts (1986) describes a small colony near Louisburg found in 1954 that was on a mainland peninsula.

This Google Earth map is a fairly accurate depiction of all past and current Leach's Storm-Petrel colonies in Nova Scotia. The data comes from Environment Canada and the Maritime Breeding Bird Atlas projects.

July 2016 Environment Canada Surveys
During July 2016, I was contracted to do alcid and storm-petrel surveys for Environment Canada. The first half of July was fairly windy and my outboard motor was in for repairs for the better part of a week. This left me with little time to get to all of the islands that I had planned on visiting.

Ram Island [43.683657, -65.029942]
Ram Island is about 800 m by 300 m, has no trees, and is 6.5 km east of Lockeport. I visited this grassy island twice this summer, once on June 25, 2016 (eBird Checklist) and again on July 30, 2016 (eBird Checklist). During the first trip I concentrated on getting accurate numbers of Razorbills (8), Atlantic Puffins (28) and Black Guillemots (73).

Atlantic Puffin on Ram Island, Shelburne County, June 25, 2016. Photo by Alix d'Entremont.

A view of Ram Island from the eastern tip looking west on July 30, 2016. Photo by Bertin d'Eon. 

Environment Canada staff had provided me with historical information that showed that in 1976 they had found 25 pairs. Breeding was not confirmed at this site during the 1986-1990 (1st) or the 2006-2010 (2nd) Maritimes Breeding Bird Atlas. It is possible that this site hadn't been checked since 1976.

During the second trip on July 30, Bertin d'Eon and I concentrated on finding storm-petrel burrows. I found a hole on the side of a small grassy hill [43.682373, -65.027917] refered to as 'Site 1' on the map below. I played Leach's calls from my Sibley's app on my phone and immediately heard a response from the burrow. Two more burrows were found at this location, one of which I felt the adult inside the burrow while no breeding was confirmed for the other. Another nearby location labeled as 'Site 2' [43.682128, -65.028361] had two potential burrows, but to breeding was confirmed since there was no response to audio and the end of the holes were not reached.

This Google Earth map shows the two locations on Ram Island, Shelburne County, where Leach's Storm-Petrel burrows were located on July 30, 2016. Breeding was only confirmed at 'Site 1'.

'Site 1' where breeding was confirmed by a response from a bird in a burrow on Ram Island, Shelburne County, on July 30, 2016. Photo by Alix d'Entremont.

A Leach's Storm-Petrel burrow at 'Site 1' on Ram Island, Shelburne County, on July 30, 2016. Photo by Alix d'Entremont.


Mud Island [43.484239, -65.988819]
Known by locals as "The Mud", this mostly forested Yarmouth County island lies 21.5 km southwest of Pubnico and is 2.7 km by 1 km at its widest. It has long been known that Mud Island was used by hundreds of pairs of Leach's Storm-Petrels. I was lucky enough to make two trips out to the island, on July 12, 2016 (eBird Checklist) and again on July 27, 2016 (eBird Checklist).

The northwestern cobble beach on Mud Island, Yarmouth County, July 13, 2016. Photo by Alix d'Entremont.

The western shore of Mud Island, Yarmouth County, July 13, 2016. Photo by Alix d'Entremont.

The results of both trips were cause for concern. No active nests were found and most nests had been dug up and the adults killed. The damage extended through the entire forested area, but the very middle was not checked. Three clues to the identification of the predator are that no tracks or droppings were found; no storm-petrel flesh or bone was present, only many feathers; and corvid feathers seemed to be a common sight near the areas of destruction. Photos of the ruined burrows have been sent around to Environment Canada and Department of Natural Resources, but no concensus has been reached. I've been told by fishermen that mink could make it to the island by hitching a ride on a loaded lobster boat on dumping day, but some feel that crows or ravens are more likely.

Leach's Storm-Petrel burrow destruction on Mud Island, Yarmouth County, July 13, 2016. Photo by Alix d'Entremont.

Leach's Storm-Petrel burrow destruction on Mud Island, Yarmouth County, July 27, 2016. Photo by Alix d'Entremont.

Leach's Storm-Petrel burrow destruction on Mud Island, Yarmouth County, July 27, 2016. Photo by Alix d'Entremont.

Leach's Storm-Petrel burrow destruction on Mud Island, Yarmouth County, July 27, 2016. Photo by Alix d'Entremont.

Stoddart Island [43.471700, -65.712889]
This forested island is about 1.75 km south of Shag Harbour, Shelburne County, and is approximately 1 km by 1.3 km in size. Bertin d'Eon and I visited the island on July 21, 2016 (eBird Checklist) and were unable to find any burrows. All burrows on the island seemed to be used by meadow voles since the entrances were smaller than those on Bon Portage and each entrance had the droppings of a small mammal. Three meadow voles were briefly seen as they scurried from one hole to the next. The Environment Canada data on Stoddart Island simply stated that Leach's Storm-Petrels were present in 2006, but gave no estimation of colony size. The island could have been abandoned by the birds if a predator made it to its shores.

Outer Bald Island [43.599588, -66.023979]
The Outer Bald Island is a grassy island about 9 km south of Comeaus Hill and is owned by the Nova Scotia Nature Trust. A trip there on July 31, 2016 (eBird Checklist), by Alec d'Entremont, Florian Schmitt, Bertin d'Eon and myself was very successful.

Eighty-one (81) burrows found, most on the northern side [43.600406, -66.024145] of the island and the remainder on the north-western corner [43.600380, -66.024782]. Most burrows were too long to reach the end with your hand.

15 burrows where the end was reached, but nothing was found.
52 burrows where the end was not reached and nothing was found.
1 burrow with 1 adult & 1 egg
1 burrow with 1 adult
1 burrow with 1 chick
2 burrows with single hatched egg
1 burrow with a bad egg.
8 burrows were less than 30 cm long.
A few (~5 burrows had two entrances)

This Google Earth map shows Outer Bald Island. The Leach's Storm-Petrel burrows were found on the northern side and northwestern corner where the cliff edges are still covered in grass.

Adult Leach's Storm-Petrel on Outer Bald Island, Yarmouth County, July 31, 2016. Photo by Bertin d'Eon.

Juvenile Leach's Storm-Petrel on Outer Bald Island, Yarmouth County, July 31, 2016. Photo by Bertin d'Eon.

Bad Leach's Storm-Petrel egg on Outer Bald Island, Yarmouth County, July 31, 2016. Photo by Bertin d'Eon.

Future Work
I will be doing more Leach's Storm-Petrel surveys during 2017 and 2018 and hope to be able to get to some islands in Halifax and Guysborough Counties as well as the Bird Islands in Cape Breton. These birds are very interesting and difficult to monitor, so I am very fortunate to have the opportunity to do these surveys.

References
McLaren, I.A. 2012. All the Birds of Nova Scotia: status & critical identification. Gaspereau Press Ltd, Kentville, N.S., Canada

Oxley, J. R. 1999. Nesting distribution and abundance of Leach’s Storm-petrel (Oceanodroma leucorhoa) on Bon Portage Island, Nova Scotia. Thesis. Acadia University, Wolfville, Nova Scotia, Canada.

Pollet, I. L., R. A. Ronconi, I. D. Jonsen, M. L. Leonard, P. D. Taylor, and D. Shutler. 2014a. Foraging movements of Leach’s Storm-petrels Oceanodroma leucorhoa during incubation. Journal of Avian Biology 45:305-314.

Stewart, R.L.M., K.A. Bredin, A.R. Coururier, A.G. Horn, D. Lepage, S. Makepeace, P.D. Taylor, M.-A. Villard, and R.M. Whittam (eds.). 2015. Second Atlas of Breeding Birds of the Maritime Provinces. Bird Studies Canada, Natural History Society and Prince Edward Island, Nature New Brunswick, New Bunswick Department of Natural Resources, Nova Scotia Bird Society, Nova Scotia Department of Natural Resources, and Prince Edward Island Department of Agriculture and Forestry, Sackville, 528 + 22 pp.

Tufts, R.W. 1986. Birds of Nova Scotia. 3rd ed. Nimbus Publishing Ltd. N.S. Museum. Halifax, N.S. 478 p.

Sunday, May 29, 2016

New Historical Record: Nova Scotia's 2nd Rock Wren

Field Encounter
On May 12, 2012, I had snapped a few photos of a wren (Fig. 1) in our Pubnico, Yarmouth County, backyard. It was an extremely rare Rock Wren, but at the time I thought it was a House Wren. I had just recently caught the birding bug and the excitement of the April 2012 fallout was still in the air. Blue Grosbeaks, Rose-breasted Grosbeaks, Indigo Buntings and even a Yellow-throated Warbler took residence in my yard following the passing of a deep, slow moving low overnight on April 22 that had produced strong winds from the Caribean and the Gulf of Mexico up to New England and Nova Scotia. The event's weather was summarized by Ian McLaren in an NS-RBA post and also treated more completely in Nova Scotia Birds Vol. 54 No. 3 pp. 42-44. Was the appearance of this wren related to this weather pattern?

Figure 1. Rock Wren in Middle West Pubnico, Yarmouth County, on May 12, 2012. Photo by Alix d'Entremont.
Identification
On May 26, 2016, David Bell was reviewing historical eBird records for Nova Scotia when he came across my photos of the wren. I had just started birding back in 2012 and had found what I thought was the closest match to this bird in the bird books. I called it a House Wren, which was also somewhat rare in Nova Scotia. He explained to me that this was a far rarer species, a Rock Wren and only the second ever for the province of Nova Scotia as per McLaren (2012). Once I took a second look, now with more experience, It was fairly obvious that this was a Rock Wren.

The features that distinguish this bird (Figs 1, 3 & 4) from House Wren (Fig. 2) are its longer bill, bold and extensive supercillium, dark legs, overall dull and more grayish plumage, buffy and un-barred flanks and shorter tail in relation to overall body size.

Figure 2. House Wren at Cape Forchu, Yarmouth County, Oct 9, 2014. Photo by Ervin Olsen.

The following are a few more photos of the Rock Wren.

Figure 3. Rock Wren in Pubnico, Yarmouth County, May 12, 2012. This angle shows the long and lightly decurved bill, the grayish brown upperparts, the unstreaked breast and the buffy flanks. Photo by Alix d'Entremont. 

Figure 4. Rock Wren in Pubnico, Yarmouth County, May 12, 2012. Notice the buffy tips of the outer tail feathers, the long bill and strong supercillium. Photo by Alix d'Entremont

Range & Migration
This wren breeds in the west from Middle America to southern British Columbia, Alberta and Saskatchewan. At present time, very little information regarding Rock Wren migration is available. Overall, it appears as though this species is a short-distance partial migrant. Most individuals from the northern part of the range as well as from higher elevations move southward during autumn. Spring migration takes place between mid-March and early May. (Lowther, Kroodsma & Farley 2000)

Vagrancy
Due to this species' limited migration, extralimital records are few, however occurances in the north east of North America have occured in Minnesota, Ontario, Massachussetts and Nova Scotia. It has also been observed in Louisiana, Alabama, Florida, Viginia and New Jersey. (Lowther, Kroodsma & Farley 2000).

The only previous record for Nova Scotia was of a bird found by John Kearney and Nancy Blair on Seal Island on Oct 4, 1980 that is recorded in Nova Scotia Birds Vol. 23 No. 1.

How did this bird get to Nova Scotia and when did it arrive? These are difficult questions to answer considering the lack of knowledge about Rock Wren migration. There are no other mentions of Rock Wren in the east in the spring 2012 issue of North American Birds, so the arrival of a bird in Pubnico was not part of a larger phenomenon. Was this a case of an initial orientation mistake made by the wren combined with the deep low pushing birds from the Gulf of Mexico up the Eastern Seaboard directly to Nova Scotia?

Ian McLaren in Nova Scotia Birds Vol. 54 No. 3 suggested that the majority of the Indigo Buntings that made it to Nova Scotia likely crossed the Gulf of Mexico during the evening of April 22 to be found from Brier Island to Halifax County on April 24. Did the Rock Wren come with the buntings or did it arrive later? Does the species use leap-frog migration where the most northerly breeders migrate the furthest south?

There are many questions but I've found few answers.

Acknowledgements
I would like to thank David Bell for his sharp eyes and identification skills which have provided me with another life bird for Nova Scotia.

References
Lowther, Peter E., Donald E. Kroodsma and Greg H. Farley. 2000. Rock Wren (Salpinctes obsoletus), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/486
doi:10.2173/bna.486

McLaren, I.A. 2012. All the Birds of Nova Scotia: status & critical identification. Gaspereau Press Ltd, Kentville, N.S., Canada

Sunday, May 22, 2016

Identification of a Gray-cheeked Thrush

Field Encounter
On May 8, 2016, Ronnie d'Entremont found a thrush lacking the chestnut tail of a Hermit and the buffy face of a Swainson's. This left him with two choices: Gray-cheeked and Bicknell's. He sent photos to Mark Dennis who felt that they best fit Gray-cheeked. By the end of the day, a few of us were able to get great views of the bird along with unobstructed photos.

Taxonony & Occurence
It was only recently when Ouellet (1993) concluded that Bicknell's and Gray-cheeked thrushes were distinct species. These two were previously considered conspecific as Gray-cheeked Thrush, consisting of three subpecies: the present day Catharus minimus minumus (Gray-cheeked of Newfoundland and n. Quebec) and C. m. aliciae (Gray-cheeked breeding from Alaska to Labrador) along with Bicknell's Thrush (Catharus bicknelli). The split was accepted by the American Ornithologists' Union in 1995.

Both Bicknell's and Gray-cheeked occur in Nova Scotia during migration, but breeding has only been confirmed with Bicknell's, mainly in the Cape Breton Highlands and formerly on our south shore islands (McLaren 2012). The second Maritime Breeding Bird Atlas found that Gray-cheeked Thrushes were probably breeding on Harbour Island, Halifax County and White Head Island, Guysborough County (Stewart et al. 2015).

Identification
Many sources state that differentiating between silent Gray-cheeked Thrush and Bicknell's Thrush in the field is difficult (Sibley 2014, Alderfer 2014...). The good quality photos of this bird in multiple positions are required in order to attempt confident identification of a silent bird. Lane & Jaramillo (2000) suggest that a broadside view under uniform lighting are required to make an accurate judgement of minute differences in colour. This was the case with this thrush as it was in the shade among willow trees producing diffused lighting. With perfect conditions and crisp photos from various angles, we have the best material to work with for a proper identification.

Primary Bases
The colour contrast between the bases of the primaries and the rest of the wing are claimed as a useful in field identification of the two species (Lane & Jaramillo 2000). In Bicknell's, the primary bases are slightly warmer and more reddish-brown than the rest of the wing. In typical aliciae Gray-cheeked, the bases are paler and appear more washed out graying-brown, while C. m. minimus have warmer brown primary bases which may be indistinguishable from Bicknell's. Figure 1 provides a nice view of the primary bases, which appear to be a paler brown than the rest of the wing without any appreciable reddish-brown, but perhaps slightly warmer than the remainder of the wing.

Underparts Colour
The flanks of Bicknell's are described by Lane & Jaramillo (2000) as reflecting the warmer brown upperparts seen in this species while contrasting more with the white belly than the washed-out, grayer flanks and belly of a Gray-cheeked. It is important to note that C. m. minumus tends to show warmer flanks than does C. m. aliciae. The contrast between cold-coloured flanks and belly (Figs 1 & 2) on the Chebogue Thrush seems minimal, suggesting Gray-cheeked.

Figure 1. Chebogue Thrush at Chebogue Point, Yarmouth County, May 8, 2016. A thrush with little eye ring, cold overall plumage and long primary extentions past the tertials. Photo by Alix d'Entremont.

Figure 2. Chebogue Thrush at Chebogue Point, Yarmouth County, May 8, 2016. The flanks appear to be less brownish than in Bicknell's and don't contrast very much with colour of the belly. Photo by Alix d'Entremont.

Upperparts Colour
Lane & Jaramillo (2000) state that the upperparts of Gray-cheeked are a monotone, cool olive-brown or grayish brown, while Bicknell's varies from a dull brown to a warm olive-brown, almost chestnut on the tail. The uppertail coverts and tail of Bicknell's is said to be a richer chestnut-brown compared to that of the Gray-cheeked that are concolorous with the back, however C. m. minimus approaches Bicknell's.

Luckily there was a Hermit Thrush at the exact same location, so useful colour comparisons can be made. It is clear that the Hermit Thrush (Figure 4) is much warmer overall and shows a clearly bright chestnut tail. Compare this to the extremely cold-looking Chebogue Thrush and you get an appreciation of how little warm browns and reds are apparent its overall plumage. Figure 3 clearly shows that the cold-coloured back of the Chebogue Thrush contrasts with the warmer tail, more reminiscent of either Bicknell's or minimus Gray-cheeked.

Figure 3. Chebogue Thrush at Chebogue Point, Yarmouth County, May 8, 2016. This photo provides a nice view of the warmer-toned tail in comparison to the more grayish-brown back. Photo by Alix d'Entremont.

Figure 4. Hermit Thrush at Chebogue Point, Yarmouth County, May 8, 2016. Note how cold-toned the upperparts of the Chebogue Thrush are compared to this Hermit Thrush.  Photo by Alix d'Entremont

Wing Ratio
While plumage and bare parts colouration are suggestive, Townsend et al. (2015) explain that vocalizations and morphometrics are much better tools for identification. Since this bird was silent, we must rely most on shape captured in the photos. Lane & Jaramillo (2000) propose that the ratio of the length of the primary extension beyond the tertials to the length of the exposed tertials might be the best way to compare the wing length of both species. They found that in Bicknell's, this ratio is 1:1 or less while in Gray-cheeked, it is 1:1 or greater. I have measured these dimensions on two photos of the thrush in question using Adobe Photoshop. The measurements in pixels as well as the resultant ratios are given below.

Exposed tertials: 243
Primaries: 311
Ratio: 1.28:1

Exposed tertials: 230
Primaries: 278
Ratio: 1.20:1

We see that the ratio matches that expected for Gray-cheeked, a result of that species' long wings. A Bicknell's Thrush was recently photographed in New Jersey and the photos allow for measurement of this ratio and produces a value of about 1:1. While the New Jersey bird doesn't show a lot of contrast between the back and tail, the upperparts are clearly warmer than that of the Chebogue Thrush. The pale base of the lower mandible of that Bicknell's is more extensive (far past the nostrils) than that of the Chebogue Thrush and seems to have a more yellow, approaching orange colouration and less fleshy tones than the Chebogue Thrush. Here, and here are a few more photos of the New Jersey Bicknell's.

Wing Morphology
Another wing feature that provides evidence of this bird's identification as a Gray-cheeked is the wing morphology. Pyle (2007) illustrates how P7 & P8 are of equal length in the folded wing in Bicknell's while P8 is longer than than P7 in Gray-cheeked. Figure 5 shows the relative length of the primaries, note how P8 is slightly longer than P7 and how P9 is hidden under P8, just like Pyle's description of Gray-cheeked.

Figure 5. Chebogue Thrush at Chebogue Point, Yarmouth County, May 8, 2016. This composite shows the wing morphology which matches Gray-cheeked more than Bicknell's. Photo by Paul Gould.

Mandible
Ouellet (1993) states that Bicknell's Thrush's bill base is bright pale yellow, whereas it is flesh or yellowish flesh in Gray-cheeked, and Todd (1963) noted that C. m. minimus of Newfoundland had a more extensive pale base than C. m. aliciae and Townsend et al. (2015) quantify this by describing that the pale extent in minimus extends beyond the nostril. The pale base to the mandible on the Chebogue Thrush pushes slightly beyond the nostril, enough to consider minumus. The colour of the pale base seems to show fleshy tones, but appear similar to some Bicknell's photos on the internet. Lane & Jaramillo (2000) do conclude that both the colour and extent of the pale base of the mandible is unreliable, so little weight will be given to it here.

Migration Timing
eBird reports along with migration timing data provides evidence in support of Gray-cheeked Thrush. As of May 8, all of the reports of Bicknell's Thrush are limited to the Dominican Republic and Puerto Rico. In contrast, reports of Gray-cheeked Thrush come from as near as New York state. The earliest arrival date of migrant Bicknell's in New England as reported by Townsend et al. (2015) is May 15. McLaren (2012) does mention a report of Bicknell's on April 23 1983 at Brier Island, but this was during an extraordinary event where numerous thrushes arrived extremely early. There was no similar event in this case, so the arrival of a Bicknell's Thrush by May 8 excluding fallouts is unlikely.

ID Conclusions
We have strong morphological evidence that the Chebogue Thrush is a Gray-cheeked. I don't feel confident in assigning this bird to a subspecies with any great amount of certainty. The back and tail of the Chebogue Thrush are not concolorous, more similar to that of minimus, but the primary bases don't appear to have any reddish-brown. The extent of the pale base of the mandible also seems within range for minimus. Due to these features, I would lean towards this being a Gray-cheeked Thrush headed to Newfoundland or northern Quebec (Catharus minimus minimus).

References
Alderfer, J., J.L. Dunn. 2014. (Ed). Complete Birds of North America, 2nd Edition. National Geographic Society. Washington DC, USA.

American Ornithologists' Union. 1995. Fortieth supplement to the American Ornithologists' Union Check-list of North American Birds. Auk 112: 819-830.

Lane, D. F. and A. Jaramillo. 2000. Identification of Hylocichla/Catharus thrushes; Part III: Gray-cheeked and Bicknell’s thrushes. Birding 32(4): 318-331.

McLaren, I.A. 2012. All the Birds of Nova Scotia: status & critical identification. Gaspereau Press Ltd, Kentville, N.S., Canada

Ouellet, H. 1993. Bicknell's Thrush: Taxonomic status and distribution. Wilson Bulletin 105: 545-754.

Pyle, P., S.N.G. Howell, R.P. Yunick, and D.F. Desante. 1997. Identification guide to North American Birds, Part 1, Columbidae to Ploceidae. Slate Creek Press, Bolinas, California.

Sibley, D.A. 2014. The Sibley Guide to Birds 2nd Ed. Alfred A. Knopf, New York, N.Y.

Stewart, R.L.M., K.A. Bredin, A.R. Coururier, A.G. Horn, D. Lepage, S. Makepeace, P.D. Taylor, M.-A. Villard, and R.M. Whittam (eds.). 2015. Second Atlas of Breeding Birds of the Maritime Provinces. Bird Studies Canada, Natural History Society and Prince Edward Island, Nature New Brunswick, New Bunswick Department of Natural Resources, Nova Scotia Bird Society, Nova Scotia Department of Natural Resources, and Prince Edward Island Department of Agriculture and Forestry, Sackville, 528 + 22 pp.

Todd, W.E.C. 1963. Birds of the Labrador Penunsula and Adjacent Areas. Toronto: University of Toronto Press.

Townsend, Jason, Kent P. McFarland, Christopher C. Rimmer, Walter G. Ellison and James E. Goetz. 2015. Bicknell's Thrush (Catharus bicknelli), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/592
doi:10.2173/bna.592

Wednesday, March 23, 2016

A Kamchatka Gull in Nova Scotia

The Meteghan Gull
Clarence Stevens Jr. notified Joan Comeau of his find of a Mew Gull (Larus canus) on Febrary 27, 2016 at the wharf in Meteghan, Digby County. The bird was re-found and photographed the next day on February 28 by Joan Comeau on the flats to the east of the wharf at Meteghan (see Google Maps). Joan sent me her photos to get confirmation on the identification and she was thrilled with my reply of "OMG. You found it!!". She had a right to be happy with her photos; there are only small numbers of Mew Gulls that winter in Nova Scotia each year (McLaren 2012). I made the trip up to Meteghan on March 13, 2016 and was able to get a few distant photos (Fig. 1). At the time of writing, the gull was last seen on March 24, 2016 by Mark Dennis and Mike MacDonald.

Figure 1. The Meteghan gull in Meteghan, Digby County on March 13, 2016. Photo by Alix d'Entremont.

The Mew Gull Complex
I wrote a blog post last year about my first North American sighting of a Mew Gull in Dartmouth. I described how the Mew Gull Complex is currently considered to be comprised of four subspecies: L.c. canus (Common Gull), L.c. heinei (Russian Common Gull), L.c. kamtschatschensis (Kamchatka Gull) and L.c. brachyrhynchus ("Short-billed" or Mew Gull). To avoid any confusion, I'll use the Latin names rather than the English names, a practice that seems more typical in Europe. The subspecies that we get in Nova Scotia each winter is canus.

At present time, the American Birding Association Checklist v. 7.8.1 from November 2015 treats all 4 taxa in the Mew Gull Complex as conspecific. Olsen & Larsson (2004) describe kamtschatschensis as distinct and the largest of the four taxa, probably requiring full species status. Some works, such as del Hoyo et al. (1996), Sibley & Monroe (1996), and most recently, Adriaens & Gibbins (2016) suggest that brachyrhynchus should be its own full species, a split that seems more likely to happen than kamtschatschensis being split from the rest.

Brachyrhynchus breeds in western North America and winters along the Pacific coast to California. Canus breeds in Europe and European Russia and winters both in the breeding area and south to the northern coast of the Mediterranean. Heinei breeds from White Russia eastwards to central Mongolia and winters in central Asia, the southern Black Sea and Caspian Sea and further south to the Persian Gulf and some make it to the coast of China. Kamtschatschensis breeds in eastern Siberia and Kamchatka and winters southwards along the coast to Japan, Korea and China. (gull-research.org)

The Gull Research Organization has a section devoted to the Mew Gull Complex complete with descriptions, measurements and many photos.

Subspecific Identification
On March 13, 2016 Ronnie d'Entremont posted photos of the Meteghan gull on the North American Gulls Facebook Page. Lou Bertalan of Germany commented that he thought the gull looked like kamtschatschensis and Maxine Quinton shared that she agreed. Once you carefully study the overall structure and mantle colour, it is evident that this bird doesn't look like canus, our default Mew Gull. Once I was alerted to the possibility of this gull being kamtschatschensis, I sent photos that I had taken on March 13 as well as the great wing photos taken by Mark Dennis on March 14 to Peter Adriaens and Chris Gibbins. Their recent paper entitled Identification of the Larus canus complex takes up 64 pages of volume 38 of Dutch Birding. It is a monumental paper that is essential to the subspecific identification of Mew Gulls.

As chance would have it, both authors were travelling together when they received the photos and suggestion that it could be kamtschatschensis. Chris Gibbins wrote on behalf of both that "the size and jizz, and the upper parts, are obviously good and everything we can see in the primary pattern looks good too." He went on to say that this primary pattern would be very rare in canus.

Elimination of brachyrhynchus is fairly easy based on size and structure which, in comparison to the Meteghan gull, would be small overall, have a rounded dove-like head, and a smaller bill (Fig. 2).

Figure 2. Brachyrhynchus in British Columbia on Sep 21, 2012. Photo by Ronnie d'Entremont.

Mantle Colour
One of the most obvious characteristics of this bird is the dark mantle. In his eBird checklist, Mark Dennis described the colour as "almost as dark as graellsii Lesser Black-backed Gull". When comparing this gull to nearby Ring-billed Gulls, the difference is striking (Figs. 3, 4). Figure 5 shows the relatively pale mantle colour of our regular winter canus, also in comparison to a Ring-billed Gull. While there is a large amount of overlap in mantle colour between Mew Gull subspecies, a dark bird such as this one seems out of range at least for canus, the palest of the four subspecies.

Figure 3. Ring-billed Gull (L) and Meteghan gull (R) in Meteghan, Digby County, on March 14, 2016. Notice the much darker mantle of the Meteghan gull compared to the Ring-billed Gull. Photo by Mark Dennis. 

Figure 4. Left to right Great Black-backed Gull, Meteghan gull and Ring-billed Gull at Meteghan on March 15, 2016. Notice the darker mantle of the Meteghan gull compared to the Ring-billed Gull. Photo by Simon d'Entremont.

Overall Size
Adriaens & Gibbins (2016) generalize that the taxa increase in size from west to east but warn that there is much variation and overlap. Brachyrhynchus is the smallest and then progressively larger are canus, heinei and kamtschatschensis. The authors compare the size of kamtschatschensis as similar to that of Ring-billed Gulls. Figures 3 and 4 show two birds of similar size, strenghtening our argument for kamtschatschensis.

Figure 5. Our regular winter canus (L) compared to a much bulkier looking Ring-billed Gull (R). Note the gentle head shape, large looking eye, visible bill band and in comparison to the Ring-billed Gull, only slightly darker mantle. Photo by Jim Edsall.

Head Shape
In comparison to the other taxa, many kamtschatschensis show an obviously long, sloping forehead and a long and strong bill giving the bird a 'snouty' impression (Adriaens & Gibbins 2016). Characteristics similar to these are more prominent in some photos than others. Figure 6 shows a more gentle looking head shape of the Meteghan gull, but still shows a larger bill and more sloped forehead in comparison to the typical small bill and rounded head of canus.

Figure 6. Meteghan gull (L) on March 12, 2016 and a regular canus (R) in Dartmouth on Feb 27, 2015. Photos by Joan Comeau (L) and Alix d'Entremont (R).

Some photos show the Meteghan gull with an extremely sloping forehead and very large looking bill (Fig. 7). This variability in appearance emphasizes the caveat that we should never rely on a single photograph when shape is an important part of a bird's identification features. Gulls, like many other species, appear to change shape with every posture.

Figure 7. The Meteghan gull on March 1, 2016, showing an extremely sloped forehead and large bill. Photo by Joan Comeau.

Head Pattern
The winter head pattern of the four taxa also differs; although we are in early spring, this feature still deserves a look (see Fig. 7). Heinei typically show a clean white head in early winter, so a late winter bird would likely show a white crown unlike the blotchy streaks on the crown of this gull. (Adriaens & Gibbins 2016)

Bills and Eyes
Most canus & heinei show a complete dark bill-band, but kamtschatschensis and brachyrhynchus both rarely show a complete band, like the Meteghan gull which has a barely visible broken bill-band (Figs. 6 & 7). Howell & Dunn (2007) describe the variation in eye colour of kamtschatschensis as dirty lemon (flecked dusky) to brownish and of the four plates of adults that are presented in their 2007 work, three appear to have irides identical in colour to those of the Meteghan gull (Fig. 8).

Figure 8. The Meteghan gull on Feb 27, 2016. The eyes are actually not entirely black; the iris in direct sunlight is brown, clearly much lighter than the black pupil. Adriaens & Gibbins (2007) found that more than 60% of the kamtschatschensis in their study had irides that were either dark or slightly paler than the pupil. Photo by Joan Comeau.

Primary Pattern
Of all four taxa, canus tends to have the most limited amount of black on P4-5, with only 9% having any black on P4 like this gull. The white mirror on P9 of canus is often larger than that of the same primary of the other taxa. An extremely small percentage (~5%) of canus show an outer web mirror on P9 that is about equal to the length of the black tip as on the Meteghan gull. These small percentages mean that canus will seldom show these wing tip features.

Figure 9. Upper side of both wings of the Meteghan gull on March 14, 2016. Photos by Mark Dennis.

Heinei shows the most black in the primaries. Figure 9 shows that this gull has a black wedge on the outer web of P6 that is slightly less than 1/3 the length of the feather, shorter than is typical in heinei (wedge covers more than 1/3). This gull has a bold white tongue tip to P7, whereas heinei usually has little or no white on the tongue tip on this primary (Fig. 15).

Kamtschatschensis, according to Adriaens & Gibbins (2006), has the most variable primary pattern, but still usually shows a combination of unique features. Most show a complete black band on P5 and some black on P4, like the Meteghan gull and 95% of kamtschatschensis show a big white tongue-tip on P7, as this gull does.

The grey tongues on the underside of the outer three primaries in kamtschatschensis average longer and wider than in heinei. In Figure 10, the Meteghan gull shows a grey tongue on P8 that is about 1/2 the length of the feather and also obvious tongues on both P9 and P10, more than in typical heinei.

Figure 10. Underside of the right wing of the Meteghan gull on March 14, 2016. Photo by Mark Dennis.

Adriaens & Gibbins (2016) warn that the main confusion taxon for kamtschatschensis in terms of primary pattern is brachyrhynchus. Applying the primary pattern identification key provided by Adriaens & Gibbins (2016) results in kamtschatschensis and this was confirmed by Adriaens (pers. comm.). The feature that potentially led away from kamtschatschensis in the late stages of the key was the apparent grey at the base of the outer web of P9 in one photo; the others show an entirely black outer web. In the photo, what looks to be a gray based outer web of P9, might actually be the inner web of P10. This makes it clear that high quality photos of the spread wings are required for accurate results from the primary pattern identification key.

Comparison Photos
Since visual comparisons have already been made with brachyrhynchus and canus, I thought it was fitting to compare the Meteghan Gull with photos of heinei and kamstchastchensis. I would like to thank AurĂ©lien Audevard, an ornithologist with the Ligue pour la Protection des Oiseaux Provence-Alpes-CĂ´te d’Azur, and Kjeld Tommy Pedersen who is a laboratory technician at the Natural History Musem of Denmark for the use of their photos. There are many more photos of all four Larus canus taxa at Gull Research Organization.

Figure 12. Kamchatka Gull (L.c. kamtshatschensis) during non-breeding season in Hokkaido, Japan on February 2, 2010. Note the large bill and sloping forehead similar to that of the Meteghan gull. The eye colour of this bird also seems to be a great match. There is no visible bill band, a feature seen in about 40% of kamtschatschensis studied by Adriaens & Gibbins (2016). Photo by AurĂ©lien Audevard.

Figure 13. Kamchatka Gull (L.c. kamtschatschensis) in Hokkaido, Japan on February 2, 2010. This view shows the tongues on the underside of the outer primaries. P10 has an obvious tongue as does P10 of the Meteghan Gull. Adriaens & Gibbins (2016) describe that about 70% of heinei show no tongue to P10. This particular kamtschatschensis does seem to show longer tongues on P9 and P8 than the Meteghan Gull. Photo by AurĂ©lien Audevard.

Figure 14. Russian Common Gull (L.c. heinei) at Sortedamssøen, Denmark on February 17, 2011. The bill of this heinei shows the typical obvious dark bill band. The barely perceptible bill band on the Meteghan gull is more similar to that of brachyrhynchus or kamtschatschensis. Photo by Kjeld Tommy Pedersen.


Figure 15. Russian Common Gull (L.c. heinei) at Sortedamssøen, Denmark on February 17, 2011. Mew Gulls (L.canus) with limited dark markings on the primary coverts are still aged as adults on the Gull Research Organization webpage. It could point to a young adult, but the primary patterns should still be representative of a full adult. Photo by Kjeld Tommy Pedersen.

Identification Conclusions
Dr. Eric Mills, a long-time birder in Nova Scotia also with world wide experience, saw this bird on March 15, 2016 and notes in his eBird checklist that "In my opinion (after looking at recent literature) only brachyrhynchus and kamschatschensis are possibilities, and this bird is far too large, too large-billed, and has the wrong head shape for brachyrhynchus." Mark Dennis, originally from the UK, confidently says that "[he has] seen many thousands of Common Gulls in Europe and some in Asia but none as dark as this." Perhaps most convincing are the comments from Peter Adriaens and Chris Gibbins, the authors of the most complete and most recent paper on subspecific identification of the Mew Gull Complex, who shared regarding the Meteghan gull that "the size and jizz, and the upper parts, are obviously good and everything we can see in the primary pattern looks good too [for kamtschatschensis]."

The Meteghan gull is clearly not brachyrhynchus, as this taxon would be much smaller overall and would have a rounded head and small bill. The mantle colour appears too dark for the expected range seen in canus. Heinei typically show a clean white crown by early winter, unlike the blurry streaked crown of this gull. The head and bill shape better fits heinei and kamtschatschensis and the bill markings are closer to that of brachyrhynchus and kamtschatschensis. The limited extent of black in the outer primaries of typical canus doesn't fit that of the Meteghan Gull which shows less black than typical heinei. The primary identification key from Adriaens & Gibbins (2016) leads to kamtschatschensis.

My own research, positive comments from local experienced birders along with thoughts from Peter Adriaens and Chris Gibbins appear to confirm the Meteghan gull as kamtschatschensis, a first for Nova Scotia.

Precedence in North America
Other east Asian gulls such as Slaty-backed and Back-tailed gulls have been found in eastern North America with some regularity. An adult Slaty-backed Gull was in Glace Bay, Cape Breton, December 2003 through February 2004 and we've had a minimum of two Black-tailed Gulls since our first was found on Sable Island in May 1997. Records of  two other east Asian gulls in Nova Scotia make our acceptance of a first record of kamtschatschensis that much easier.

Outside of Alaska, reports of kamtschatschensis are very rare, but there are multiple well studied birds in blog sites and eBird that are listed below with links to documentation.

Rhode Island - January-February 2006
Ontario - March 2006
Illinois - February 2008
Ontario - November 2009
Massachussetts - 2010
Massachussetts - 2013
Newfoundland - September 2014 (Birding with Buckley)
Massachussetts - March 2015
Connecticut - April 2015 (eBird checklist 1, eBird checklist 2)

Acknowledgements
I would like to thank Peter Adriaens and Chris Gibbins for their expert comments on the photos that I had sent to them. Maxine Quinton carefully read every word of a draft of this blog and provided me with many excellent suggestions that were incorporated in the final version. Thank you to Joan Comeau, Ronnie d'Entremont, Mark Dennis, Jim Edsall, Simon d'Entremont, Aurélien Audevard and Kjeld Tommy Pedersen for their excellent photos.

References:
Adriaens, P. & C. Gibbins. 2016. Identification of the Larus canus complex. Dutch Birding 38:1-64.

del Hoyo, J., A. Elliott & J. Sargatal, eds. 1996. Handbook of the birds of the world, vol. 3. Lynx Edicions, Barcelona.

Howell, S.N.G. and J. Dunn. 2007. Gulls of the Americas. Houghton Mifflin Company, New York, N.Y.

Howell, S.N.G.,  I. Lewington & W. Russell. 2014. Rare Birds of North America. Princeton University Press

McLaren, I.A. 2012. All the Birds of Nova Scotia: status & critical identification. Gaspereau Press Ltd, Kentville, N.S., Canada

Olsen, Klaus Malling, and Hans Larsson. 2004. Gulls of Europe, Asia and North America. London: Christopher Helm.

Sibley, CG and BL Monroe. 1996. Birds of the World, on diskette, Windows version 2.0. Charles G. Sibley, Santa Rosa, CA, USA

Monday, March 7, 2016

Aberrant Red-tailed Hawk

A Partially White Red-tailed Hawk in Yarmouth
A few images of an intriguing Red-tailed Hawk were posted to the Nova Scotia Bird Society Facebook page by Robert Surette. The hawk was photographed on March 4, 2016, soaring above the Town of Yarmouth and Robert was fortunate enough to capture both the underside (Fig. 1) and upperside (Fig. 2) of this magnificent bird.

Figure 1. Aberrant Red-tailed Hawk in the Town of Yarmouth, Yarmouth County, March 4, 2016. Notice the asymmetric pattern to the white flight feathers. Photo by Robert Surette.

With a quick glance, it almost looks like the bird is missing many secondaries and primaries (Fig. 1). If a bird were moulting flight feathers, the same feathers would be replaced at the same time on both wings, creating symmetry in the feather gaps. Upon closer inspection you see that there are no gaps, the feathers are actually present, but they appear entirely white. See my previous post named Ghost Grackle for some introductory information on colours and colour aberrations in birds.

Figure 2. Aberrant Red-tailed Hawk in the Town of Yarmouth, Yarmouth County, March 4, 2016. This view of the upperparts of this hawk shows that is it mostly white. The head and tail appear normally coloured, as do some of the flight feathers.  Photo by Robert Surette.

The aberrant feathers appear entirely white. There is no indication of any pale brownish or greyish feathers. Aberrant feathers are known to bleach quickly; this requires checking of feathers that are protected when the bird perched for an indication of what a feather looked like when it was new. The secondaries of a Red-tailed Hawk are covered when the hawk is perched, and these feathers also appear to be pure white from below (Fig. 1) and from above (Fig. 2).

This hawk is definitely not an albino. This requires that all feathers lack both melanin pigments, which would render a Red-tailed Hawk's plumage entirely white. We can also eliminate all other aberrant conditions except leucism and progressive greying due to the fact that the unusual feathers appear pure white and not brown or grey. These two remaining conditions are difficult to tell apart if all feathers are affected. Luckily, this is not the case here. When leucism affects only part of the bird's plumage, the pattern produced is typically symmetrical. As previously mentioned, the pattern is asymmetrical. The differences between the wings are annotated by arrows in Figure 3. (Grouw 2013)

Leucism almost always affects the extremities (outer primaries, head, feet, belly...), so a bird showing many white feathers on the back and few in the wing along with normally coloured outer primaries, head and belly is likely not a leucistic individual. Progressive graying is also documented to occur with some regularity in Red-tailed Hawks. (van Grouw, pers. comm.)

The left wing has only one white outer primary (P10) while the right wing has three (P7, P9 & P10). There are also clear differences between each wing in the secondaries, the right wing having a large patch of white feathers not present in the left wing.

Figure 3. Aberrant Red-tailed Hawk in the Town of Yarmouth, Yarmouth County, March 4, 2016. This view of the underparts of this hawk shows that the white feather pattern is not bilaterally symmetrical. We also see that the head, body and underwing coverts appear normally coloured.  Photo by Robert Surette.

This pattern of white feathers is characteristic of the colour abnormality called progressive greying, a condition that is more common than leucism. Progressive greying arises once a bird reaches a certain age and is specifically the progressive loss of pigment cells with age. Once the condition begins, the bird will gain an increasing number of white feathers after every moult until the entire plumage is white. (van Grouw 2013)

History of White Red-tailed Hawks in Nova Scotia
Red-tailed Hawks with white plumage have been documented fairly regularly in Nova Scotia. See the list below for NS Birds issues from Jan 1997 until today with mention of white Red-tailed Hawks. All but the latest issue include a link to the PDF on the Nova Scotia Bird Society website. Follow the link to read about the sightings.

NS Birds Vol 57 No 2 (Fig. 4)

Two long-staying birds were at Sheffield Mills from 1988 until 1996 and the Wolfville/Hortonville area from 2001 until 2010 (Fig. 5). Some other white Red-tailed Hawks have been spotted in Kingston, Kings Co. in 1998; Meiklefield, Pictou Co. in 1998; Pomquet, Antigonish Co. in 2007; West Hants in 2008 and the recent bird at Canning in November 2014 (Fig. 4).

Figure 4. A mostly white Red-tailed Hawk at Canning November 6, 2014. Without better photos, we can't be sure of the exact condition, but it is likely leucism or progressive greying - the affected feathers do look pure white. Photo by Mel Carlton.

Figure 5. White Red-tailed Hawk at Grand PrĂ© in November 2009. The feet and eyes of this bird appear normally coloured, so it isn't an albino. The affected plumage appears pure white, so again it is likely caused by leucism or progressive greying through a lack of melanin. Photo by Tuma Young.

The Christmas Bird Counts in The Valley have consistently produced a relatively high number of Red-tailed Hawks in comparison to the rest of the province. A higher number of birds would definitely give an observer a higher chance of spotting an aberrant Red-tailed Hawk.

In the process of researching this hawk, it has been clear that most of the birding community in North America hasn't jumped on van Grouw's aberrant colour mutation terminology. While both leucism and progressive greying produce plumage and skin that is all white or partly white through a lack of melanin, they do differ in that leucism's effects on an individual does not change over time while progressive greying's effects on the bird's pluamge spreads over time.

References:
Grouw, Hein van. 2013. What colour is that bird? The causes and recognition of common colour aberrations in birds. British Birds 106: 17-29.