Bird Habitat Preferences: Nesting Species

by Carl Strang

It’s axiomatic that you can’t understand wildlife without understanding habitat: the kinds of places animals need for food, shelter, all the requirements for survival. Last week I presented summaries of habitat data for fox and gray squirrels at Mayslake Forest Preserve. Today I want to share results for two species of birds that nest at Mayslake, one a year-round resident, the other a neotropical migrant.

Downy woodpeckers are year-round residents in our area.

An association between downy woodpeckers and wooded habitats is to be expected. On the other hand, they also go out into open areas to forage, as I have noted in their attention to goldenrod gall flies. Do the birds show a particular pattern of preference? I have two full years of data, and have divided them by season: December to February, March to May, June to August and September to November. The downies proved to be pretty consistent among seasons. I had few observations in open habitats. The birds’ presence in savannas was roughly in proportion to their area in most seasons. Though the forests are poor, as I mentioned in the context of the squirrels, they are the preferred hangout for Mayslake’s downy woodpeckers.

If all the data are combined, I observed downy woodpeckers in open areas 4 times, in savannas 213 times, and in forests 197 times. These counts have to be compared to the expected observations based on the acreage of each habitat type. If the woodpeckers divided themselves in proportion to habitat areas the counts would have been 128 in the open, 178 in savannas, and 108 in forest.

The migrant species I considered was the Baltimore oriole.

The Baltimore oriole winters in the tropics. They are on their way back to us now, but won’t arrive for another month or so.

Here the total counts of orioles were 2 in open habitats, 57 in savanna, and 43 in forest. Expectations if the birds weren’t picky are 32, 44 and 26. Wooded habitats interest the birds but open areas are avoided. There may be a slight preference for savanna over forest in these data; certainly nearly all the nests I have found have been in savanna areas.

I looked at two other bird species, both winter residents that nest north of here, and I will share those results tomorrow.


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