Olive-sided Flycatcher Species Dossier

December 13, 2012 at 7:12 am (birds, species dossiers)
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by Carl Strang

This week’s species dossier is for contrast. Though I have seen olive-sided flycatchers in several spring migration seasons in recent years, I have not been able to add anything significant to the first account I made in 2000. Prior to then, I had heard one calling its “quick three beers!” at Maple Grove Forest Preserve one spring in the mid-1980’s. I have never observed them in their North Woods breeding grounds, and I have not observed them during the fall migration.

Olive-sided flycatcher

Olive-sided flycatcher

Flycatcher, Olive-sided

25MY00. Willowbrook. Olive-sided flycatcher foraging from branches high in dead trees. Its bill is enormous, and its head large, giving it a distinctive look. This one was yellow in vent area. It was distinguished by the lack of an eye-ring and wing bars, along with the narrow light-colored channel between the dark sides of its breast. It never vocalized.

And that’s it. I have seen the species again at Willowbrook, at Fullersburg, and at Mayslake, but the story always has been the same. I limit the dossier to observations I have made myself. Of course, those observations are informed by what others have discovered, in this case that the large muscular head is an adaptation for crushing the hard exoskeletons of bees, wasps and other armored insects upon which this flycatcher feeds. Such prey become more active and abundant later in the season, so this species is one of the later migrants. I have never heard one call other than that one time in the 1980’s.

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Birds, Buckthorn and Oaks

May 22, 2012 at 6:02 am (birds, ecology, restoration)
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by Carl Strang

Now that the early part of the migration season is past, I can do a preliminary test of the Birds-Buckthorn-Oaks hypothesis. The idea is that migrating birds seem to prefer buckthorn infested woodlands early in the migration season because the buckthorn understory provides shelter unavailable in restored, oak-dominated woodlands because usually the oaks have not yet leafed out to provide food and shelter. Data from last year supported this idea, because late-season migrants showed a shift from the buckthorns to the newly leafing oaks. This year a further, better test was made possible by the warm early season stimulating oaks to break buds early, so that they were well in leaf for the early part of the migration season. So, what did the data show? I compiled the numbers of neotropical migrants that don’t nest on Mayslake Forest Preserve that I counted prior to May 19 (when oaks began leafing last year), comparing last year’s counts to this year’s. The results were stark: I counted only 5 of those birds in the buckthorn woodland, compared to 22 in the restored savannas (compared to 80 and 34, respectively, last year. Numbers were low this year, in part because my back strain limited my outings, but also a lot of migrants seemed to be bypassing Mayslake).

Things are moving along. This olive-sided flycatcher, a late season migrant, stopped by Mayslake on May 14, earlier than usual.

Using last year’s proportions to calculate expected values if there had been no difference between years, the values would have been 18.9 in the buckthorn-dominated woodland, 8.1 in the savanna. It should come as no surprise that the resulting chi-squared test statistic showed a highly significant difference (34.07, even with only 1 degree of freedom, is far above the threshold). With the migration progressing so rapidly, I don’t know if there will be enough observations in the late season to consider separately, but if so there will be an additional post. Either way, I am satisfied that the data support my point.

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Mayslake Birds Update

June 2, 2009 at 11:11 am (birds)
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by Carl Strang

Spring migration is nearly done. This was my first at Mayslake Forest Preserve, and I was pleased to find that the preserve hosted a wide range of species stopping to refuel on their way north. I was not very successful in photographing them in the late part of the season, however. One reasonably decent exception was an olive-sided flycatcher.

Olive-sided flycatcher 1b

This north woods nester has a large head in comparison to other flycatchers, the extra jaw musculature needed to crunch its preferred diet of bees, wasps and other relatively hard-shelled insects. This diet also accounts for the olive-sided’s late appearance in the migration season. Don’t expect to find it by its distinctive song. I have heard the “quick-three-beers!” in DuPage County only once in more than 25 years. Its preferred hunting perch is a high dead tree branch, which makes it fairly easy to find when it is present.

Nesting continues. My count of first-round robin nests reached half a dozen on the preserve, and they have been fledging young for the past week. Soon they’ll begin round two. A few mallard and Canada goose broods have made regular appearances around May’s Lake and Trinity Lake.

Goose family b

A pair of phoebes is nesting at the friary.

Phoebe nest b

I taped over the unoccupied chambers of the purple martin house, leaving open the two with starling broods.

Starling nestlings b

Purple martin colonies are few in our area, but this house is in a good location and there is hope that young birds will find it attractive in June.

Martin house 1b

With the migrants refueled and on their way, my attention will focus more on the preserve’s nesting residents. Among them, I hope, will be this yellow-billed cuckoo.

Yellow-billed cuckoo 2b

The cuckoo was foraging at the edge of the savanna, where the gypsy moth eggs have hatched.

GM eggs hatched 2b

Cuckoos are caterpillar specialists, and may be attracted by the gypsy moths.

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