We keep records of bird sightings not just to tally our life, state, year and other lists, but also to keep track of bird populations, their comings and goings, etc.
Migrant birds in our area seem to arrive in a fairly predictable progression - Ospreys, followed by Eastern Phoebes, then Palm and Pine Warblers, Blue-Gray Gnatcatchers, etc. But the phases can vary a fair bit in time.
Last year, for example, by the first of April we had seen Gnatcatchers, a few warblers, and multiple species of Swallows. This year, it's a week later in the year, and those species are just starting to dribble in. Spring has been late a-coming, and those birds aren't dummies - they need insects to eat and warm southerly winds to speed their journey north and save energy.
With all this in mind, Lisa and I went to Flag Ponds Nature Park in Calvert County yesterday to herald the opening of warbler season. With the help of her magic (that is, birdsong on Sibley's iPhone app) we brought in that Pine Warbler above, and this lovely creature: