Friday, Jun 01 2012

The Avian Rights of Spring

by Jan D. Axtell, Staff Naturalist

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The spring migration of birds, to me, is the really one best times of the year to bird watch. In my mind it is one of the quintessential barometers of the season. Not only are birds arriving in the area to breed, but there are also those that are passing through to points north. If you are up early in the mornings, and have been paying attention over the last couple of weeks you will have noted the remarkable change in our local forests. It is at this time of year that every bird will be making themselves known and setting up shop for the summer. Over the last few weeks I have been watching the different species trickle back up north and listening to the rising cacophony of bird music in the mornings.


We are fortunate, and have a great diversity of birds in our northern forest; an embarrassment of riches so to speak. Many of these birds travel great distances - from as far as Latin and South American- to breed, raise young, and live out their summer here in the Northern Hardwood Coniferous forests of the Green Mountains.


Upon arrival they start picking out habitat on which to stake their claim. The strongest individuals are most likely to grab the best territories. Meaning they are able to exclude their competitors (within species) for the prime spots. This ultimately gives them access to the best food, cover, and vantage point from which to attract the opposite sex. The birds use many strategies to decide who gets what. Often times, as in the case of the Red Winged Blackbird, it is a matter of who gets there first. Older males migrate before the females and young males. They get the pick of the territories.


Other strategies include ritualized display or mocked battle as in the case of the Wild Turkey. You very well may have seen the big Toms out in one of the local fields puffed up, displaying their tail fan, and strutting trying to attract the attention of the congregated hens and discourage the advances of rival Tom’s and the immature Jakes.


The competition for the prime breeding territories is tough, but it insures that the strongest individuals in a population have the greatest chance to bring off a brood in the best habitat available. It is this intra-specific competition that drives the evolutionary process and naturally selects the strongest possible individuals to succeed in their efforts to pass on their genetics to the next generation.


Once breeding territories have been established the business of attracting mates begins and this is typically done through song and ritual display. Go stand outside your back door and listen. I guarantee that you will hear some bird trying to attract the attention of a mate. Go out side in the early morning or later in the evening and you will hear a great deal more. If you visit any marsh, watch for the male Red Winged blackbirds flashing their red shoulder patches. The field at the corner of Moulton Ln. and Stagecoach Rd. has a couple of breeding males that have already set up territories across the pond from each other and you can watch them posture and show off their red epaulets warning each other to stand clear of each other. This simultaneously tells rivals that they are on his turf and signals, in conjunction with song, the attention of the females he hopes to breed with. In the case of the ruffed grouse he drums his chest with his wings to attract attention and mark his territory. This sound can travel over a half mile and is one of my favorite displays. I like the fact that human males are not the only ones who beat their chest and make noise to attract the attention of the ladies.


Feather plumage is another factor in which mates are selected. In most cases the males are the one trying to attract the attention of females. Subsequently, male plumage is much more ornate and colorful to visually attract females. Birds like the Northern Cardinal, the Scarlet tanager, Wood duck, and Indigo bunting all have very colorful plumage. It is one of their strategies in attraction a mate.


The female’s plumage are considerably more drab which camouflages them while they sit on nests. It’s a neat dichotomy. Males the bright colors to attract attention and females need the camouflage to hide and protect the nest. The irony is palpable.


Habitat selection, breeding plumage, song, and ritual display all combined help decipher who are the strongest individual during a breeding season. It is what drives and molds the populations of birds we have in the northern forests and this is the prime time to visit the marshes, woods, and fields to view them in action. By choosing different habitats one can maximize the diversity of birds they see and by paying close attention one can witness bird behavior at its most intense.

 

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