I did some early-morning birding at Wooded Island last week. It was a very unpromising morning: there was an icy wind out of the northeast, overcast skies--a typical spring day in Chicago. A wind off the lake usually means terrible birding along the lakefront.
The parks and beaches are way stations for northbound migrants. Most birds migrate at night; when the sun comes up, they start looking for a likely place to touch down for a day of rest and feeding. The city on one side and the lake's deep waters on the other squeeze them into the narrow strip of parks.
A northeasterly wind may physically push them west to the valleys of the Des Plaines and Fox rivers. Or maybe they just won't fly into the teeth of a freezing gale. For whatever combination of reasons, places like Montrose Harbor and the Lincoln Park Bird Sanctuary at Addison are usually dead when the cold northeast winds blow.
On days like that, Wooded Island is usually much more birdy (current birder-speak for places that consistently attract birds). The reasons are not hard to see. When Frederick Law Olmsted was designing Jackson Park for the World's Columbian Exposition of 1893, he decided to leave part of it in a somewhat natural state to provide a place with a "secluded, natural, sylvan aspect" that would be a refuge from the crowds and bustle on the rest of the exposition grounds.
Jackson Park was at that time a natural landscape featuring three long sand ridges running parallel to the lakeshore. These low ridges were once shorelines of Lake Michigan and its immediate postglacial ancestor, Lake Chicago. Between the ridges were low, marshy swales.
Olmsted did not like the site. He wanted one farther south, but the Illinois Central vetoed it because they didn't want to extend their tracks. Writing in Inland Architect magazine, Olmsted commented acidly on the tendency of "town governments, when they find bodies of landÉnot favorable to the ends of dealers in building lots, to regard them as natural reservations for pleasure grounds."
But Olmsted was a landscaping genius--he also designed Central Park in New York and the White House grounds--and he came up with a graceful plan based on the natural contours. He deepened the swales into lagoons, elevated the ridges, and made all of the exposition buildings accessible by both land and water. Wooded Island was a piece of ridge that he left pretty much alone, except for the addition of native trees, shrubs, and flowers gathered by Olmsted's crews in Illinois, Indiana, and Wisconsin. The big oaks and cottonwoods that still dominate the island were planted by nature and left untouched by Olmsted.
The lush plantings are still around. They provide enough cover to sustain nesting wood ducks, yellow warblers, warbling vireos, and green-backed herons. For migrants, the island has enough food and cover to support them for days at a time while they wait for the wind to change.
Nonetheless, I was not expecting birds to be dripping from the trees, and my expectations proved to be accurate. As my friend Dave Standish and I crossed the Clarence Darrow Bridge onto the island, we did see a pair of Canada geese on the grass at the edge of the lagoon, hear a cardinal singing in the brush, and watch both barn swallows and rough-winged swallows feeding over the water.
These are all nesting species at Wooded Island. So far, we hadn't seen a single migrant. Once across the bridge, we saw another probable resident, a warbling vireo. We finally got our first migrants a few yards down the walk when our approach scattered a large flock of white-throated sparrows that were feeding on the grass.
White-throated sparrows are not exactly rare birds around Chicago during migration. They are a north-woods species and they pass through here in very large numbers in both spring and fall. The males sing during spring migration, a clear, high whistle that New Englanders have long translated as Old-Sam Pea-bo-dy, Pea-bo-dy, Pea-bo-dy.
The date was the only unusual thing about this sighting. The peak time for white-throated sparrows is the end of April. By the middle of May, their numbers should be much reduced. We should have been seeing a few white-throated sparrows and large numbers of their close relative, the white-crowned sparrow, a slightly later migrant. We eventually heard a couple of white-crowns singing and also saw a few, but the relative proportions of the two species were more like May 1 than May 14.
Then, a hermit thrush--the first of two we would see--flew up onto a park bench. This was another bird long past its time. Hermit thrushes usually start coming through in mid-April. By mid-May, Swainson's thrush should be the common species, but we saw none of these.
Normally, weather has only a very modest effect on the timing of migration. Warm weather early in spring can bring a few species north early, but since most species are far to the south at that time, they wouldn't know what the weather was like here unless they happened to be picking up Channel Nine on cable.
The birds also have to wait for their food sources to emerge. Arboreal insect eaters like vireos and warblers follow the opening leaves north, because the insects come out to feed on the leaves. Weather can speed up or slow down leaf emergence slightly, but the lengthening days are the major control on that process, so weather, again, plays only a minor role.
But this year is different. The unrelieved dominance of cold high-pressure air during the entire first half of May has created a very obvious delay in the spring migration. And wind direction is probably more important in that delay than temperature. Birds flying north in spring tend to wait for southerly winds. When a front moves in from the south, the birds ride it north. To an observer on the ground, the spring migration seems to proceed in a series of waves; we see large numbers of birds each time a warm front passes through, and then there is a lull until the next front arrives.
So far, May has not given us a single warm front. We have had no waves of migrants. The birds are way behind schedule. Consider the warblers. Dave and I didn't see our first one until we were halfway around the island. And the first one we saw was a palm warbler, a species that is among the earliest arrivals in its family. Our total for the day was seven species. Normally, even a poor day in May at Wooded Island will produce 12 to 15 species.
Our one good bird was a cerulean warbler that was kind enough to spend some time in the lowest branches of a hawthorn shrub in full flower. Ceruleans have backs so blue they practically glow, but they are treetop birds who often show us nothing but their bellies. This time, Dave and I got a good look at the blue back.
Ceruleans are birds of mature forests. The galloping destruction of tropical forests has sent them into a decline that has now lasted 20 years. Sightings are growing ever rarer, and I savor each one I get.
The big question now for local birders is when we will finally get a break in this persistent weather pattern. It could be that zillions of birds are hanging out in Tennessee or some other place in that general neighborhood just waiting for a strong southern wind to carry them to their nesting grounds.
If the weather broke just right, we could get a huge fallout of birds, a month's worth of migrants all arriving on the same day. It is every birder's wish that something like that will happen, and especially that it will happen on a day when work or other inescapable obligations don't interfere with getting out to see the birds pass through. Imagine waiting all spring for a really good birding day and then having to spend it sitting at a desk.