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.

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.


  1. Good stuff, Alix. The turned up soil reminds me of crow damage on various golf course throughout NS.

    John Loch

    1. Thanks John. I'm leaning towards corvids rather than mammals.

  2. In late August 1992 I heard the cackling sounds of Leach's coming from somewhere near our cabin on Camp Rd., Brier Island, several times at night. I mentioned this to Louise Garron, a local lady with a cabin nearby, and she described swallow - like birds that were black and white, and made weird noises, flying around the trees nearby, behind her cabin at night. I was able to point out the sounds to a visiting birder, Don Shanahan, from Ontario, early that Sept.. At the time, Marion Zinck (? now Marion Munro) had been camping at the end of Gull Rock Road doing a plant survey for much of the summer, and told me that she had heard the calls at night coming from the wooded area between the Flat Grounds and Hogyard Cove, that and the previous summer.. She was familiar with them, from her visits to Bon Portage with Acadia U. They have not been seen or heard since then (personal obs, and fide Eric Mills' Birds of Brier Island), but to me this is all tantalizing evidence that a few might have nested around the S.W. end of Brier during that period.

  3. Thank you for sharing your excellent blog about these wonderful, amazing birds. I have long loved the LSPEs on BPI, Alix, and have seen the colonies burrow locations change somewhat through the years since 1984. Regarding predators, I saw a Greater Black-backed Gull holding a Leache's storm Petrel sitting on the roof on a house on Cape Sable Island just across the from the road to the Lobster Pound. The petrel seemed to be still alive when the gull first landed, and the gull quickly began to devour it. The photos of predation look to be the work of Crows. There was a large nest near the trail to the Gunning Camp, and always lots of feathers there, too. Ingrid's work is very interesting, and valuable to our understanding of the petrels travels. Thanks!

    1. Thanks Joan. I saw a crow attacking a LSPE on BP a few years back. I look forward to next year's surveys.

  4. Great job Alix. In 1984 I worked for DNR or at the time the Department of Lands and Forest as a summer student. Myself and another guy named Dale did Island inventories for part of the summer off of Stonehurst and MaHone Bay. At the time on Big Duck Island we had about 1500 Leaches Storm Petrel Burrows. I haven't been out to the island since, so I don't know the current status.

    1. That's fascinating, James. It would be great to get recent data on Big Duck Island.

    2. James, the only information that I've got on Big Duck Island is that they were present in 1984. Thanks for providing that estimate of 1500 burrows. I'll try to get out there in the next two summers, but it'll have to be a nice day to get there and land.

  5. Thanks for publishing your results, Alix. Your readers will be looking forward to next year's reports on the LSPE.

    You mention the number of 50,000 breeding pairs for BPI, is that number remaining stable over the past couple of decades, I'm wondering. And hoping it is.

    On the other hand it is discouraging to see the numbers decreasing in areas of smaller populations where they were formerly doing well. It seems that if the numbers dip below a certain level, predation from gulls and corvids can be the tipping point on a colony. If the numbers are above a certain level, this kind of predation will not have a devastating impact I would think, as nature tends to balance things out. In a colony of thousands the impact will be less meaningful than if there are only dozens of pairs. It does look like certain colonies of LSPE are in jeopardy. I hope next year you will be able to gather more information to fill out the picture. Good work!

    1. I think you're right Carmel. It is likely a numbers issue where small colonies are hardest hit due to high percentage loss compared to larger ones. Thanks for the comments and interest.