on the edge

Tromping around Weaver Dunes, south of Wabasha MN, for 8 hours trying to identify every bird we could find was exhausting but rewarding, and what an absolutely beautiful day to participate in The Nature Conservancy’s bird blitz on May 12.

Cape May Warbler-

First bird of the day — Cape May Warbler, high in a leafy tree (bane of photographers — the tree, not the bird)

The spring migration was running a little behind schedule, but we managed to find (and identify) 58 species (which admittedly doesn’t sound like a lot for 8 hours of work).  We explored a variety of habitats, but the best places to look were edges between shrub and forest, or prairie and forest.

Yellowrump Warbler-

Yellow-rumped Warblers outnumbered other warbler species, and thankfully posed at much lower elevations in the trees.

Rose-breasted Grosbeak-

We only saw one Rose-breasted Grosbeak, and he was quite shy about coming out in the open to show off his raspberry bib.

Lark Sparrow

Lark Sparrows were more common than the warblers, flashing their white outer tail feathers as they flew. True to their name, their song is much more of a warble than a buzz — i.e., lark-like.

Lark Sparrow

Lark Sparrows typically nest in shrubs and forage in grassy areas removed from the nest. They have the unusual habit of walking, instead of hopping.

Northern Waterthrush-

Down at the edge of a small pond, a Northern Waterthrush hunted for insects.

Northern Waterthrush-

A distinctive eyestripe and wagging tail made this large warbler easy to identify.

Brown Thrasher-

A Brown Thasher was very uncooperative about posing, and remained hidden in the dense foliage of trees in the grassy savannah.

Baltimore Oriole-

Orioles foraged high in leafy treetops, but were easy to find by listening for their characteristic song.

Gray-cheeked Thrush-

Another edge-lover found skulking among the low vegetation in the woods surrounding a pond was the Gray-cheeked Thrush, with its characteristic white eyering.

Our efforts were added to those of the birders walking other TNC properties throughout the tri-state region of MN, North Dakota, and South Dakota.  Together all observers on May 12 found over 200 different bird species, or approximately 50% of those known to reside or pass through MN on migration in May.  Not bad…it’s a nationwide competition, so we’ll see how MN bird numbers stack up with those elsewhere in the U.S.

Considering that our American birds have to navigate and survive stormy weather and drastic climate changes, glass windows and glass-covered buildings, marked habitat alterations, and depleted food supplies from all the pesticide and herbicide applications, it’s a wonder that we see the diversity that we do.

Watching for warblers

Spring starts and stops here; it can’t seem to really get going.  As a result, leaves have been slow to develop and that makes it a little easier to spot the flighty little warblers as they migrate through.  In fact, the cold weather seems to have slowed their normal migratory rush down a little.

Our strange spring weather and the numbers of new warbler species arriving daily means that we often get multiple species flitting around in the backyard on any given day.  Watching the warblers go about their daily hunt for food is a great illustration of a classical ecological study I learned about many years ago — Robert MacArthur’s study of niche partitioning in warblers to reduce competition.  He found that several warbler species could co-exist if they harvested the resource in different ways or from different areas of the tree.

From Biocyclopedia - Animal Ecology

From Biocyclopedia – Animal Ecology

A few examples to illustrate how one basic body type of small insectivore has specialized to divide up the food resource:

Yellow-rumped Warblers pretend to be flycatchers, “hawking” insects from the air or gleaning them from the terminal ends of branches of shrubs or trees, often flitting from the bottom to the top of one tree, or the top of one to the bottom of another.

yellow rumped warbler-male-2

Orange-crowned Warblers poke around in the leaf litter on the forest floor or into the newly emerging clumps of leaves on the branches of shrubs.

female orange crowned warbler

Black and White Warblers are nuthatch-“wannabes”, foraging upside down along the trunk and large branches of big trees.  They are constantly on the move and really hard to get in focus.

black and white warbler

Yellow Warblers prefer to forage among the branches of shrubs and trees along streams or other wetland areas.  Their bright color really makes them stand out among the willow branches.

yellow warbler

Ovenbirds and Waterthrushes are the largest warblers and prefer to forage in damp, swampy marshes or moist forest floor.

northern waterthrush

Those are just the ones I have seen in my backyard so far.  There are still more species arriving to fatten up for the last push toward the breeding grounds in the Canadian coniferous forest. Hopefully, I will get some photos of them too.