Sunday, March 20, 2016

Of Pine Warblers and Phoebes

Deep in a protected forested cove of old growth bur oaks, spring ephemerals are well advanced for mid-March. I missed seeing the trout lilies in bloom here, with only the mottled leaves left carpeting the forest floor. Spring beauty, rue anemone and even a couple of bluebells were in bloom this week in the Ozarks. It may be a record for early blooming exotic species such as Bradford pear, which stick out along fencerows and in yards. I have not yet seen shadbush flowering, and most other natives are still waiting for reliably warm weather to bloom. The wisdom of the natives.

The pine warblers and Eastern phoebes returned to Missouri in recent weeks, their calls some of the signature sounds of spring. Birds are triggered to migrate by day length, which means they normally show up when there is abundant food available to rear their young. The warm weather may be pushing up spring flora, but the oaks, which provide a significant source of food by way of insect life for breeding birds, are still dormant, allowing for the spring annuals to have ample light for their life cycles. The ancient rites of spring events including bloom period and bud break may be early for some species, but hopefully not everything. The timberdoodles have been around for several weeks now and in great abundance in certain parts of the Ozarks. Lizards and snakes are starting to come out to take advantage of the warm weather. But as I write, an inch of snow rests on the ground in Jefferson City while all the Bradford pears are in full bloom.

When we think of breeding birds, timing really is everything. There have been several studies investigating nest success as it pertains to the effects of climate change and earlier spring. Considering that much of the biomass consumed by baby birds comes in the form of caterpillars, and many of them loyal to oaks, the earlier warmer spring weather is triggering the earlier maturation of caterpillars. By the time the birds arrive for nesting, many caterpillars are already moths, not the same nutritious and available food as they were in caterpillar stage. Spring birders of talk about "warbler neck," a condition one develops after long hours of looking towards towering canopies for the warblers gleaning insects from the buds of trees. With migratory songbirds declining across their range, potentially from a number of factors including climate change and the disruption of natural cycles, we may have to start looking harder for those signature signs of spring like the colorful warblers passing through on their way to Canada.

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