Robyn Perkins

LSLBO Bander-in-Charge

June 10 was the final day of Spring Migration Monitoring for the Lesser Slave Lake Bird Observatory. It was an unusual end for the season because a cougar was spotted too close for comfort, so we decided to pack it in a little early.

Aside from the abnormal cougar encounter, hot temperatures, thick smoke, and notably early leaf-out, spring migration was roughly average. Few species arrived earlier than normal, and most species followed their typical migration trajectories. In total, 146 bird species were identified this spring from over 45,000 bird encounters. The observation highlight was our first ever turkey vulture. This large scavenging bird prefers open agricultural lands but may become more common since we are seeing an increase in encounters of other birds also more commonly associated with southern Alberta, such as gray catbirds and Baltimore orioles.

We finished the season without any particularly thrilling days of overhead migration where we may sometimes count over 20,000 geese or 3,000 songbirds in a single day. Without these big days, Spring 2023 counted nearly 20,000 fewer birds than Spring 2022. Of all the unusual environmental conditions, I suspect that the one with the largest influence was not the smoke and fires, but the unseasonably hot temperatures. If fires interfere with local migration, we often see days of heavy foraging and birds heading back south. We did not record these much this year. Instead, our decreased counts may be because during hot periods overhead migration takes place during the cooler nighttime hours when we cannot count.

While perhaps too hot to migrate in, the weather was favourable for netting and only five days saw no capture efforts. In total, we banded 989 birds from 50 species – just above the average of 950 birds of 46 species banded per spring. The top-banded species was American redstarts with 143 banded, followed by white-throated sparrows in second with 98 banded, then myrtle warblers with 84, Swainson’s thrushes with 70, and alder flycatchers with 66 banded.

The capture highlight was our first MacGillivray’s warbler of spring and only the third banded by us after two were banded within hours of each other in the fall of 1997. This is a common warbler species in British Columbia that does not normally stray into Alberta much farther than the Rocky Mountains. They are named after the Scottish naturalist William MacGillivray by John Audubon, even though another ornithologist had already named this species the ‘Tolmie’s warbler,’ in honour of the versatile fur trader, surgeon, and politician William Tolmie. They look incredibly similar to the mourning warbler, which breeds locally. While some mourning warblers lack the white ring of feathers around their eye, many females can have a thin whitish eye ring that can surround the eye. In contrast, this eye ring is always present, thick, white, and does not wrap completely around the eye in MacGillivray’s warblers.

With spring migration monitoring complete, we now turn our efforts to monitoring our breeding populations with our Monitoring Avian Productivity and Survivorship (MAPS) program.

The third-ever MacGillivray’s warbler banded at the LSLBO.