Using a Decoy to Study Endangered Warblers

BANDING GOLDEN-WINGED WARBLERS

By Michael Davenport, Marine Species & GIS Programs Manager

Conserve Wildlife Foundation Intern, Nelson Melendez, and I recently had an opportunity to assist Endangered & Nongame Species Program Biologist Sharon Petzinger in her research on golden-winged warblers, a species just added to the state’s list of Endangered species this year.  We were banding males which had been observed previously and had already claimed breeding territories.  They were being banded in order to obtain data regarding their distribution and habitat use, as well as other life history information.

Only males were being targeted for banding.  Males are territorial during the breeding season and do not tolerate the presence of other male golden-winged warblers.  Therefore, in order to catch a male, we would use their own territorial instincts to lure them into a mist net (a mist net looks a little like a volley ball net with much finer netting which becomes invisible to birds if set-up properly).

Once a mist net was set-up near a known golden-winged’s territory, Sharon used a custom-painted “toy” bird to play the role of an unwelcome male visitor.  She also used a call play-back, a recording of a male golden-winged’s song.  The song would lure the male near the net, and the decoy should bring him right into the net.

We went to several locations in northwest New Jersey where golden-winged warblers had been observed earlier in the year to set-up the mist net.  On this particular day, however, luck was not with us for no golden-winged warblers were caught.  Several other species were captured however, such as a veery, chestnut-sided warbler, and a Brewster’s warbler.  The Brewster’s warbler is actually a hybrid of a golden-winged warbler and a blue-winged warbler.  Another hybrid form between those two species is known as Lawrence’s warbler.

The veery and chestnut-sided warbler were released from the net unharmed.  Before the Brewster’s was released, a small aluminum band was placed on its leg and measurements such as wing length and weight were taken.

Warblers are often an overlooked group of birds by some birdwatchers due to their small size and relative difficulty in observing.  They are stunningly beautiful however, which becomes apparent when you have the opportunity to view them up-close.  They are a very diverse species group with a variety of interesting life histories.  There is currently one species (the golden-winged) listed as Endangered in the state and 11 additional species listed as Special Concern.  To learn more about them, please visit our on-line field guide links below.

NJ’s Rare Warblers

Golden-winged Warbler (Vermivora chrysoptera)
Blackburnian Warbler (Dendroica fusca)
Black-throated Blue Warbler (Dendroica caerulescens)
Black-throated Green Warbler (Dendroica virens)
Canada Warbler (Wilsonia canadensis)
Cerulean Warbler (Dendroica cerulea)
Hooded Warbler (Wilsonia citrina)
Kentucky Warbler (Oporornis formosus)
Nashville Warbler (Oreothlypis ruficapilla)
Northern Parula (Parula americana)
Worm-eating Warbler (Helmitheros vermivorum)
Yellow-breasted Chat (Icteria virens)