July 21, 2013

With heat, will warblers stay in tune with migration?

Walking in the woods has been so hot lately that it’s hard to stay upbeat. But this week I was perked up by a small, blue bird.

I was surprised at how close this small bird allowed me to get before flitting off. Being a relatively inexperienced birder, I came home to the books and found out my hiking companion was a male black-throated blue warbler.

The Smithsonian’s Bird Migration Center reports that forest warblers are relatively tame, which was definitely true of this one. I was able to get very close to him and get a good look at his coloring and size. He didn’t sing but I was able to check the website at Cornell Lab of Ornithology to hear his song. I have heard this bird’s call before but not known what it was. Seeing him has made the song easier to connect to the singer.

Black-throated blue warblers winter in the Caribbean islands like Cuba, Jamaica, Hispaniola and Puerto Rico. They return to the same territory — sometimes even the same bushes — for summer breeding and nesting in the northeastern United States and southeastern Canada. 

They typically mate with the same partner although mortality and other circumstances may cause them to find a new partner. Males are a mixture of blue, gray and white. Females are gray and green.

Black-throated blue warblers nest in upland forests, using hobblebush, striped maple and other shrubby understory plants for nest sites. Nest predators include squirrels and chipmunks but also bigger birds like crows and jays. Although nest robbers may prey on eggs and nestlings, black-throated blue warblers, like other songbirds, may make a new nest and start another brood if food resources — insects and spiders — are sufficient.

It will be interesting to see if the heat and high humidity will change migration patterns this year. It’s possible the weather will induce them to stay longer as insect prey populations thrive in the North Country “tropical” conditions.

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