Wednesday, April 11, 2012

Bluebirds Begin Their Nest and the Visiting Fox Sparrow

A pair of Bluebirds has begun using a nestbox in our largest field. For the last 2 days the female of the pair has been bringing nest material into the box. The male doesn't assist her in her efforts, but he remains nearby and sometimes acts like a one bird pep rally –perching on top of the box, calling and fluttering his wings.
The female Bluebird at the nestbox entrance
The female takes fairly frequent breaks from her task of collecting tufts of dry grass in order to hunt for food. Although the prey couldn’t be more different, the hunting technique used by Bluebirds is rather like that employed by some raptors; they perch on a small sapling or on a thick plant stem and watch the meadow below them for beetles or grubs. When they spot something moving, they fly down to snatch it up, much like a raptor would do with a mouse.
The male Bluebird surveys the meadow from the top of a fence post
The male divides his time between coaxing the female to work (although she doesn’t seem to need it), hunting for food and singing territorial proclamations from various perches. The Bluebird's song is a soft sweet warble, and one that is synonymous with a spring meadow.
Occasionally the male will be seen giving a tribute to the female. I remember once seeing a pair of Bluebirds on top of their nest box: the male had caught a large Junebug and was set on giving it to his mate, but he couldn’t quite get himself to part with it. He’d begin to pass it from his beak to hers, but as soon as she bit into it, he start to pull it away. What began as a nuptial gifting session turned into a domestic tugging match. I imagined him saying something like: “Sweetie, just let me take back this one Junebug, and I’ll get you something else –something just as nice!”
Th at Junebug tribute was finally handed over to the female
There is a pair of Tree Swallows claiming the box right next to the Bluebirds’ house.  In these early days of neighbor to neighbor relations, things are a bit tense, and there have been some territorial squabbles –mostly over who is doing what in whose yard. The Tree Swallows have a great predator alert system –one that I should think the Bluebirds can only benefit from. Whenever a hawk (usually a Red-tailed Hawk or a Northern Harrier) shows up anywhere over the field, all of the area’s swallows start twittering and mobbing the intruder—escorting the hawk out of the vicinity if possible. Sometimes several dozen swallows take part in this type of operation. The swallows’ relatively small size and their swift, erratic motions in the air make it look like the hawk is flying through a swarm of unusually large mosquitoes.
Watching for insect prey
At the wooded margins of the large field, I hear the somber and notably slurred notes of a Fox Sparrow. No, this guy is not drunk on fermented berries or anything like that. His whistled song just makes him sound like he’s a bit tipsy. This beautiful reddish brown migrant sparrow is more typically seen around bird feeders in the early spring, but not this year. Instead, the Fox Sparrows seem to prefer to kick up their own meals out of the leaf litter. The temperatures have been on the cold side lately, but the ground has been snow-free, so finding food in the wild has been pretty easy for these guys.
The visiting Fox Sparrow
From a distance the Fox Sparrow’s ruddy colored back and tail, and his relative large size may lead you to think that he’s some kind of thrush. His heavily spotted breast is somewhat thrush-like as well. However, his short conical bill makes clear his family lineage resides with the finches. 

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