Birds, Buckthorn and Oaks Final

by Carl Strang

As I mentioned in my previous post on this subject, the songbird migration was nearly done by mid-May. In fact I have only 3 observations to add to the ones from the early part of the season, two in the oaks and one in the buckthorn-dominated woodland. That mildly reinforces my earlier conclusion, that the only reason buckthorn woodlands appeal to birds early in the season in our area is that oaks, which dominate most of our woodlands, leaf out late. In this year when the oaks were in leaf throughout the migration season, songbird migrants nearly abandoned the insect-depauperate buckthorn at Mayslake Forest Preserve and spent their time in the oak woodlands.

South savanna at Mayslake, showing oaks well leafed.

So far all the analysis has been of the total species counts of neotropical migrants that do not nest at Mayslake. However, some of those species are brush specialists that might be expected to prefer the buckthorn over the more open oak woodlands regardless of what is happening in the canopy.

The Tennessee warbler is an example of a canopy species, on the other hand, which will not want to spend a lot of time foraging down in the buckthorn, though they might want to have it handy for resting and as a refuge from predators.

When I look at the two years’ data, sorting out brush from non-brush birds, the most curious observation is that hardly any brush-loving birds stopped by Mayslake this year. Only two birds out of the total sample of 30 were of brush species. Last year, 38 of 166 were brush birds. Looking at 2011, then, both brush and non-brush birds preferred the buckthorn woodland early in the season, though the preference was stronger for the brush species. Late last year, after the oaks were leafing out, non-brush species preferred oaks while the brush birds did not show a strong preference for either woodland type.

All of these data, coming as they do from one site over a short period of time, amount to a pilot study at best. Nevertheless, they support the notion that the apparent preference of migrant songbirds for woodlands dominated by invasive shrubs is an illusion. Birds avoid the buckthorn and prefer restored native woodlands when the latter are in leaf, capable of providing both food and essential shelter.

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1 Comment

  1. June 7, 2012 at 5:37 am

    […] As I mentioned when summarizing data on bird preferences for buckthorn vs. oak woodlands, this year was characterized by a number of migrant species bypassing Mayslake altogether, so there were many for which comparisons could not be made. Share this:FacebookEmailLike this:LikeBe the first to like this post. […]


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