Thursday, August 18, 2016

Pubnico Pelagic 2016

The yearly Pubnico Pelagic occured on August 13, 2016 this year. See Pubnico Pelagic 2014 and Pubnico Pelagic 2015 for the previous two years' blog posts. I also create a YouTube video for each trip, the 2016 video can be seen below, or follow this link Pubnico Pelagic 2016.



This trip is cause for excitement many months before we actually leave the wharf. It is a chance for those of us who rarely go offshore to get close-up views of many species that are only specs on the horizon when viewed from land. This year I had already seen both species of storm-petrel, a Pomarine Jaeger (eBird Checklist) and the four expected species of shearwater (eBird Checklist) on previous trips. This meant that most species that we would see wouldn't be new ticks for the year for me.

Cory's Shearwater (borealis subspecies) at German Bank, August 13, 2016. Photo by Alix d'Entremont.

An Audubon's Shearwater was photographed near Grand Manan on August 11, 2016, and a South Polar Skua was observed on a Brier Island whale trip on August 12, 2016. These two sightings combined with the very warm sea surface temperature maps (20 degrees Celcius just west of NS) seemed to suggest that we had the chance of finding something big.

Ronnie d'Entremont organized the trip again this year and Steven d'Entremont captained the Rebecca Lynn I. The boat left at about 5:30 am from Dennis Point Wharf in Lower West Pubnico. Below is a list of the participants:

Ronnie d'Entremont
Raymond d'Entremont
Paul Gould
Eric Mills
Bruce Stevens
Alan Covert
Ken McKenna
Kevin Lantz
Larry Neily
Mark Dennis
Mike MacDonald
Jane Alexander
Keith Lowe
Reinhard Geisler
Lori Mathis
Jerry Mathis
Graham Williams
Peter Brannon
Diane LeBlanc
Liz Voellinger
Simon d'Entremont
Alix d'Entremont
Peggy Scanlan
Chris Pepper
Angela Granchelli

Some of the crew; left to right: Mark Dennis, Ken McKenna, Liz Voellinger, Chris Pepper, Eric Mills, ?? and Raymond d'Entremont. Photo by Alix d'Entremont.

The first interesting observation of the trip were of shearwaters in Lobster Bay, before we even reached the Mud Islands. The Bon Portage crew regularly get good numbers of shearwaters passing by the island, so seeing them in Lobster Bay isn't really unexpected.

We took the opportunity to sail near to Round Island on our way out to sea. Bruce Stevens spotted a Black-crowned Night-Heron as it flew over the island. I am almost convinced that these rare Nova Scotia breeders are nesting on nearby Mud Island. I had one on Round Island in 2012 (eBird) and another three earlier this year (eBird). It has or currently does nest on Seal Island and islands near Cape Sable Island (McLaren 2012). Breeding of this species has been confirmed again this year on Bon Portage Island (eBird), where it has been breeding since 1977 (McLaren 2012).

Once we passed the Mud Islands, a few of us thought we saw a few Manx, but they were too distant to be sure of the identification. A Cory's was also likely seen fairly early, but it too was gone before anyone else got to see it.

We often hear of migrant birds landing on boats that can be many miles offshore. On this trip, we had three species of Passerine that were sighted quite far from land: Barn Swallow, Yellow Warbler and Brown-headed Cowbird. The cowbird flew 3 or 4 circles around the boat as two dozen birders watched it. We assumed it would try to land, but it flew off and returned later to circle the boat again without landing.

Brown-headed Cowbird, hatch-year Barn Swallow and Yellow Warbler, August 13, 2016. Photos by Alix d'Entremont.

My first ever Lesser Black-backed Gull was one seen on the Pubnico Pelagic in 2012. That first bird was an adult while the one seen during this 2016 trip looked like an second-cycle type bird with still juvenile looking inner primaries. It appears to be finishing its second prebasic moult as it is growing the outer primaries and inner secondaries.

Lesser Black-backed Gull at German Bank, August 13, 2016. Photo by Alix d'Entremont.

I spotted the only Northern Fulmar during the entire trip when it was a little distance away. It did fly in a bit closer, but only gave us one chance for photos. The Great Shearwaters outnumbered the Sooty Shearwaters with a ratio of ??.

Northern Fulmar at German Bank, August 13, 2016Photo by Alix d'Entremont.

Sooty Shearwater at German Bank, August 13, 2016Photo by Alix d'Entremont.

Great Shearwater at German Bank, August 13, 2016Photo by Alix d'Entremont.

At first, the only storm-petrels that we had were Wilson's, but finally, Mark Dennis yelled out Leach's and we got some great views of both species to compare size, markings and flight style. Ronnie commented that photographing these tiny pelagic birds is similar in difficulty to "trying to eat jello with chopsticks". I agree.

Wilson's Storm-Petrel pitter-pattering on the water's surface at German Bank, August 13, 2016Photo by Alix d'Entremont

Leach's Storm-Petrel at German Bank, August 13, 2016Photo by Alix d'Entremont

The two other expected species of shearwater obligingly showed themselves. The first was a Cory's Shearwater (Calonectris diomedia) spotted by Dr. Eric Mills that gave us adequate underside views to eliminate the C.d. diomedia (Scopoli's) which has yet to be photographically confirmed in Nova Scotia. See the first photo in this blog post for an underside view of this Cory's. A sight record of Scopoli's exists from Sable Island in September 2015 (eBird Checklist) and Mills et al. (2015) summarise the issue in an issue of NS Birds. The British and Dutch authorities have separated the two as distinct species, Calonectris diomedia (Scopoli's) and Calonectris borealis (Cory's), but in North America, they remain as subspecies.

Cory's Shearwater at German Bank, August 13, 2016Photo by Alix d'Entremont.

Rounding off the four expected shearwater species was an extremely confiding Manx Shearwater. These small shearwaters typically only give brief views, and from my experience, aren't attracted to chum as much as the others. This Manx came in to the chum, at one point sitting on the water less than 10 feet from us. We watched as it circled the boat and dove completely in the water for a number of seconds. It was diving underwater when the other larger birds like Herring Gulls would fly in to steal the fish pieces that the Manx was trying to catch - a great technique for evading the bullies.

Manx Shearwater at German Bank, August 13, 2016Photo by Alix d'Entremont.

Manx Shearwater at German Bank, August 13, 2016Photo by Alix d'Entremont.

Manx Shearwater at German Bank, August 13, 2016Photo by Alix d'Entremont.

Manx Shearwater at German Bank, August 13, 2016Photo by Alix d'Entremont.

I thought I had 3 Black-legged Kittiwake recently from Outer Bald Island, but they were a few kilometres away, so I couldn't really rule out Bonaparte's or other small gulls, so didn't add them to my eBird checklist. I needed the species for my year list, so the adult that gave a good show was my first of the year.

Adult Black-legged Kittiwake at German Bank, August 13, 2016Photo by Alix d'Entremont.

A Northern Gannet came in for some chum so we got good fews of hooks with lead weights that were caught in its webbing. It also seemed to have an issue with one of its wings. After having observed the quick and agile Manx Shearwater, this gannet appeared gangly and uncoordinated as it went for the pieces of fish just below the water's surface.

Adult Northern Gannet at German Bank, August 13, 2016Photo by Alix d'Entremont.

Northern Gannet with line, hooks and lead weights caught in its webbing at German Bank, August 13, 2016Photo by Alix d'Entremont.

eBird Checklists:

Leg 1 (5:30-6:30)
Leg 2 (6:30-7:30)
Leg 3 (7:30-8:30)
Leg 4 (8:30-9:30)
Leg 5 (9:30-10:30)
Leg 6 (10:30-11:30)
Leg 7 (11:30-12:30)
Leg 8 (12:30-13:30)
Leg 9 (13:30-14:30)
Leg 10 (14:30-15:30)

Below is a list of all species and total count during all legs of the trip.

Species Name / Species Count
American Black Duck 1
Common Eider 49
Northern Fulmar 1
Cory's Shearwater 2
Great Shearwater 544
Sooty Shearwater 28
Manx Shearwater 1
shearwater sp. 2
Wilson's Storm-Petrel 20
Leach's Storm-Petrel 3
storm-petrel sp. 2
Northern Gannet 65
Great Cormorant 1
Double-crested Cormorant 112
Great Blue Heron 2
Black-crowned Night-Heron 1
Bald Eagle 2
Black-bellied Plover 8
Ruddy Turnstone 4
Least Sandpiper 17
White-rumped Sandpiper 3
Semipalmated Sandpiper 7
peep sp. 31
Short-billed Dowitcher 2
Red-necked Phalarope 79
Red Phalarope 400
Red-necked/Red Phalarope 416
Pomarine Jaeger 1
Razorbill 2
Black Guillemot 275
Atlantic Puffin 110
alcid sp. 2
Black-legged Kittiwake 2
Herring Gull 410
Lesser Black-backed Gull 3
Great Black-backed Gull 280
Common Tern 8
Arctic Tern 2
Common/Arctic Tern 21
American Crow 4
Common Raven 9
Barn Swallow 2
swallow sp. 3
Yellow Warbler 1
Brown-headed Cowbird 1
passerine sp. 1

The hopes of a "mega", a very rare bird, did not materialise. The sea surface temperature as measured by our boats instruments was only about 13 degrees Celcius, much cooler than what was displayed on Rutger's SST maps. It was a very pleasant trip in terms of sea conditions and weather and it was a pleasure to get to see birders that I rarely bump into. I'm looking forward to next year's trip.

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

Mills, Eric L., Bruce Stevens & Jim Wilson. 2015. Cory's and Scopoli's Shearwaters - a Challenge for Atlantic Canadian Birders. NS Birds Vol. 57, No. 4. pp. 38-43.

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