Sunday, May 5, 2013

Brown Thrashers and Rufous-sided Towhees - Also Some New Blooms in the Old Forest

A newly arrived Brown Thrasher sings from a tree top
The male Rufous-sided Towhee arrived  over a week ago
Almost every day brings at least one newly arriving migrant to the nature preserve. Today a half dozen different warbler types were seen in our old woods. Last week among the new comers were the Brown Thrasher and the Rufous-sided Towhee. These are 2 unrelated species that look very different but have very similar lifestyles and breeding habitat requirements.
The thrasher is one of the Mimic Thrushes - they imitate the songs and calls of other birds
The towhee was once called "Ground Robin" for their reddish flanks and ground feeding habits
It has been tough going for the thrasher and the towhee in recent decades as their preferred habitat (brushy meadow) disappears throughout much of their range. By its very nature, over-grown meadow habitat is only temporary; it’s a habitat that is in the process of transitioning from meadow into forest - and so the end result of this natural succession process is to exclude both species from breeding there. So in order to keep the birds happy, it is necessary that there are always new farm fields and pastureland being abandoned and allowed to grow in.
2 young sibling thrashers pal around together in mid summer
An adult thrasher defending the nest area and giving loud "smack" calls
With habitat requirements like these, a valid question would be to ask whether the towhee or the thrasher could have been all that common before Europeans cleared the original forests of Eastern North America. Before that time these birds, and many others that share similar habitat requirements, would've been reliant on other disturbance factors in the environment – factors such as forest fires, blow-downs and of course, beavers. All of these factors would serve to clear land of its forest cover and thereby allow the natural field succession process to commence.
A female towhee (with brown head) has a beak full of caterpillars meant for its hungry brood
An immature towhee seen in mid summer - note the nondescript plumage
It is likely that Native Americans also played a large role in providing the thrasher and the towhee with habitat – as they regularly utilized fire and other techniques for clearing land. Natural forest edges occurring around wetlands and some geological features would've also provided a certain amount of habitat for these birds, but again, not enough to make either species very common.
Thrashers feed on insects, fruit and will come to bird feeders for peanuts
This immature thrasher lacks the yellow eye color of the adult
I think that it is doubtful that pre-colonial disturbance factors would've provided enough habitat to make thrashers andtowhee very common in that remote past - at least in the Northeast, but that would be impossible to confirm since no detailed records regarding songbird populations were kept at that time. It is however pretty likely that we are heading back to a population density that is more in keeping with what it was in the pre-colonial period. 
The towhee can be a common visitor to bird feeders
At the Nature Preserve, our own habitat for towhee and thrasher is in very good shape and it’s likely to remain that way for some time even with little intervention from us. This is because of the incredibly slow rate in which some of our old farm fields are reverting back to forest. Erosion and 2 centuries of agriculture rendered some of these hillside fields inhospitable for even the heartiest pioneer trees and shrubs; the result of this will be to extend the these fields’ “brushy period” for another couple of decades and thus keep the land in suitable condition for these 2 wonderful resident songbird species.
Toad Shade Trillium
And extended period of warmer than average temperatures has accelerated the leafing out of the forest and the blooming of the woodland wildflowers. Many flowers have opened early and have had shorter than normal bloom periods. 
Red Trillium
A rare yellow form of the Red Trillium - now protected in a shade garden
Wild Ginger grows as a spare ground cover in one of the woodland gardens
Twin Leaf - enjoys a particularly short blooming period
False Rue Anemone - one of our rarest forest flowers
Cut-leaf Toothwort
Perfoliate Bellwort
Dutchman's Breeches
Squirrel Corn

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