Thursday, April 14, 2005

A Swainson's Warbler in NYC

Swainson's Warbler (Limnothlypis swainsonii)


Photographed near Forest Park water hole
(Photo credit - Steve Nanz)

It has been an unusual start to the spring songbird migration. There have been numerous sightings around the five boroughs of southern warbler species. Prothonotary and Yellow-throated Warblers breed in states south of New York but on occasion overshoot their range and end up in city parks. When they do show up it is mainly at the end of April and they are few and far between. For reasons that I don’t think we’ll ever know there have been several individuals of both species seen in Brooklyn, Queens, Manhattan and Staten Island this month. The most unusual arrival, however, has been of a Swainson’s Warbler in Forest Park, Queens. Bull’s Birds of New York State describes this species as a “very rare” migrant overshoot.

Unlike most of the other North American Wood-Warblers the Swainson’s Warbler is understated in coloration and markings. It skulks around on the ground foraging for worms and insects under the leaf litter. Within their typical range I’ve been told that they are not easy to watch. I’ve never seen one and recent Internet reports describe an individual that is very accommodating allowing long periods of observation.

-click to learn more about the Swainson's Warbler-

Shane was working at the airport in Queens and agreed to pick me up if I took the subway to Forest Hills after work.

American Smoketree buds (Cotinus obovatus)

(Photo credit - Rob J)

We arrived at Forest Park at about 4:30pm. Al Ott was present with four other birders and told us that we just missed the warbler. It had flown off about 30 minutes before we arrived so he took us to the spot where it was last seen. We walked up the rise from the water hole to search the forest’s thick leaf litter north of the swampy habitat. We were talking for about 10 minutes when I swear I watched the Swainson's Warbler emerge from under the leaves. It was only about twenty feet from where we were standing. Is it possible that it had been taking a siesta under the leaves? It hadn't flown in to that spot. I had been watching the small opening in the forest as we talked and it was exposed enough that I should have noticed it.

As reported by others, the olive-brown and gray bird appeared to be relatively tame. Most birds that feed in the leaf litter grab the leaves and toss them out of the way. The Swainson’s Warbler, however, gently lifted each leaf, peered underneath it for food then placed it back down. We stayed for about forty-five minutes and the whole time it remained in close proximity to our group. One behavior I hadn’t seen reported online is its curious habit of quivering the rear of its body. The head remained motionless but the tail and rear moved so quickly that it looked like it was shivering. The Dunn and Garrett "Warbler" guide only makes brief mention of this behavior. One guess would be that it functions to flush up insects. I located a study of their foraging behavior online where the biologist describes the unusual vibrating and how it may help in finding food.

-click to learn how they forage-

There’s always something new...

Tuliptree bud (Liriodendron tulipifera)

(Photo credit - Rob J)

1 comment:

Anonymous said...

Rob,
excellent reference on the foraging behavior of the SWWA. None of my guidebooks mention it, but it was quite clear to me that the rapid vibration should be pretty effective in getting critters out from under the leaves.
Roberto

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