ALWAYS IN SEASON: Late May brings most bird species

The bird world reaches maximum species diversity at this time of year.

That's another way of saying that there are more different kinds of birds around now than at any other time of year.

This creates a great deal of excitement among bird lovers.

The week brought excited reports from readers who'd recognized goldfinches for the first time, as well as from those who'd just found a rare warbler.

Actually, by this morning -- Sunday -- we are probably past maximum diversity.

The early part of last week brought an extraordinary number, and variety, of warblers, and the weather Monday and Tuesday forced them to suspend their northward journeys. Wet, cold weather meant the warblers needed to feed heavily, and so many left their usual haunts in treetops and alighted on the ground.

This year's "warbler fall" wasn't as spectacular as one that occurred several years ago, but it was memorable nonetheless.

It produced one rarity, yellow-throated warbler, a vagrant here. This bird was well-seen and well-documented -- but I missed it.

There were larger than usual numbers of Blackburnian warblers, a regular but uncommon species here -- and always a spectacular bird.

So, it was a good week to run up the warbler list.

Not everyone has such a list, of course. Warblers are a kind of Holy Grail among birders.

Most of the continent's half-a-hundred species are brightly colored, although some are drab. All are small. And most are denizens of the treetops, so they are often hard to see -- and gazing up to find them produces something called "warbler neck."

What's more, warblers don't come to feeders, although they are sometimes attracted to water sources.

So, they don't automatically show up in backyards.

Good warbler-watching is dependent on weather conditions, too. Some years, southeast winds sweep the warblers northward, and few stop in our area.

Other years -- this among them -- strong low-pressure systems force warblers to take a break in migration.

These variables make warbler watching something of a specialty because it takes patience -- and time.

Warbler-watching is best in spring because many more species pass through our area as migrants than stay as nesting species.

Most of them move through our area as southward migrants, too, but in the fall, warblers are uniformly drab birds -- so much so that most bird books devote a special section to "confusing fall warblers."

Fortunately, peak species diversity includes birds that are easy to see. The migration of orioles probably reached its peak last week, and some watchers reported dozens of Baltimore and orchard orioles at feeders offering sweetened water, oranges or grape jelly.

Ruby-throated hummingbirds come to feeders offering sweetened water, too, and my impression is that our own modest feeding effort attracted more hummingbirds this spring than in any other that we've spent at our place west of Gilby, N.D.

All the hummingbirds, the orioles, the warblers, didn't produce the excitement generated by a single indigo bunting.

This happened in an odd way.

At midweek, a grandmother called to say that she and her granddaughter had seen a beautiful blue bird, and that they'd been able to identify it in the bird book as an indigo bunting. It was a first sighting for both of them, and both of them were excited.

When I got home that night, I made a quick inspection of the bird feeders, as I usually do, and of the lawn, garden and shrubs near the house.

Sure enough, I saw an indigo bunting. Indigo buntings are regulars here, but I am always delighted to see one. The indigo bunting is a sparrow-sized bird. As its name suggests, it is blue overall, but the hue depends on light conditions. Often, it is quite bright; sometimes the bird has a dark blue, almost inky aspect -- the condition implied by the term indigo.

For me, the importance of this week's indigo bunting was something else, however. It provided additional evidence of the birding adage that you see what you think about.

The fact that the indigo bunting was on my mind may have made me better able to see and identify it among a swarm of other finches and sparrows -- part of the week's peak species diversity.

Jacobs is publisher and editor of the Herald.