Signs of Spring in the Natural World
Hopefully you have been enjoying the increased daylight - I know I have. And boy, you can really feel it right in the pineal gland, right? Ok, maybe not. But more than you realize, this obscure gland buried deep inside your brain is changing you and the world around you every day in response to changing day length, otherwise known as photoperiod. One of the more obvious and fun examples of this is through increasing bird song.
In people, the pineal gland, which is ultimately connected to the retina through a complex neural pathway, produces the hormone melatonin during periods of dark. This, in large part, regulates our circadian rhythms. But in birds, melatonin actually causes the song control structures of the brain to develop in response to increasing photoperiod, which is what’s happening right now. In birds, day length also regulates the growth of reproductive organs, which I guess you could say exhibit annual shrinkage each winter, when they’re not needed.
I should probably get back to bird song. If you are paying attention, you many have noticed that certain birds have indeed been ramping up their singing lately. Northern Cardinals are known for their backyard-brightening color at this otherwise bleak time, but their increasing bouts of song also improve the ambience here in, dare we say, “late winter”. Listen for duets, because male and female cardinals both sing, perhaps in an attempt to determine their compatibility.
Tufted Titmice, those plain but charming birds of backyard feeding stations, have also gotten quite vocal in recent weeks. The classic mnemonics for their two note refrain is either “peter, peter” or “here, here”, and these can be heard echoing forth from woodlands and yards everywhere right now, with the exception of Nantucket, which they have never managed to colonize.
Maybe the loudest of the locals belting out more tunes right now is the Carolina Wren. Compact but powerful singers, these relatively recent colonizers of the northeast were uncommon this far north when I was a kid. Now you can hear their performances in just about every backyard thanks to our winters being warmer, on average. These strict insectivores sometimes visit suet feeders but seem to do just fine searching out insects and their eggs and larvae in leaf litter and on bark. If you’re not sure what they sound like, check out this singing male who is eventually joined by a calling female.
While these repetitive two or three note songs seem simple, males have repertoires of up to 55 song types, plus several types of calls. When males encounter an unknown individual, they rapidly sing several song types, and if the intruder doesn’t immediately respond with a female call, they attack. Despite their pugnacious nature, these engaging and animated birds are happy to nest around and even inside human structures, like under propane tank lids and in old sheds and garages. If you leave a window open for a few days you might even end up with Carolina Wrens as roommates - there are records of them nesting inside a plastic cup in a bathroom and in a hole in an old couch. But unless you like really loud roommates who may occasionally attack you, I would try to avoid rooming with these guys. Just enjoy their increasingly lusty songs from the other side of the window, and try to share in their hormonally induced hope that spring is on the way.