Olive-Sided Flycatchers Cease to Refuel

29 August 2023

Olive-sided flycatchers (Contopus cooperi) are uncommon birds in Pittsburgh. Not solely have they declined 78% since 1970, however they’re solely current on migration after which only one or two per season. When three people had been discovered on the identical day, Friday 25 August, in Allegheny County it was uncommon certainly. These three weren’t the identical fowl:

  • Sewickley Heights Borough Park at 8:20am, seen lately on Monday 28 Aug
  • Hartwood Acres, Saxonburg Fields at 10:50am
  • Homewood Cemetery at midday

Although olive-sided flycatchers nest from Alaska to Newfoundland and southward into the Cascades and Rockies, not a lot is understood of their migration routes. Within the fall the japanese birds usually circulation westward inside Canada, then grasp a left at Minnesota and migrate by way of the Nice Plains and japanese Rockies. You may see their relative abundance from the third week of August by way of the third week of October on this slide present.

Olive-sided flycatcher weekly relative abundance from eBird Status and Trends

Alaska’s breeding olive-sided flycatchers are declining quickly and have one of many longest migrations of any flycatcher — from Alaska to Peru. Migratory stopover websites are crucial for his or her survival however no one knew the place they went so a study team, headed by Julie C. Hagelin, determined to trace the birds’ migration by catching them in mist nets and attaching geolocator backpacks.

What they found when the birds returned is that Alaskan breeders fan out throughout the Rockies on their approach south, some as far east as Texas, earlier than they head by way of Mexico to South America. Additionally they discovered 13 necessary stopover websites which are important to the birds’ survival on migration. Their favourite spots are barely completely different in Central America in fall versus spring. Two of the 13 websites are within the U.S. Cascade Mountains. All of the websites are on these maps.

(illustration from DeGruyter: Revealing migratory path, important stopovers
and non-breeding areas of a boreal songbird in
steep decline

Pittsburgh by no means figures closely within the olive-sided flycatcher’s journey agenda although this yr we gave the impression to be a beautiful stopover. Our birds in all probability come from breeding websites in japanese Canada.

Are our olive-sided flycatchers stopping on the similar locations in Central America because the Alaskan group? We received’t know till some runs an analogous examine in japanese Canada.

(picture from Wikimedia Commons, abundance maps from eBird, stopover maps from DeGruyter; origin hyperlinks are within the captions)

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