It’s a Leaf! No, Wait…

An American autumn. Fall, if you will be colloquial. I expected it to be much like ours, only with reliable weather, and therefore more reliably gold-burnished leaves, crunching deliciously underfoot. And a few extra pumpkin and spice baked snacks thrown in for good measure, though I’m pleased to say that delectable combination has rather caught on back across the pond too.

Imagine, then, my dismay at finding myself gasping for air in the midst of a baking hot, stickily humid Indian summer. In the middle of last week the temperature soared into the 80s (it sounds so much more impressive in good ol’ archaic Fahrenheit), and on a lunchtime walk at a local nature park the birds were clearly in hiding as a result. Instead, every small patch of daisy-like flowers was abuzz and aflutter with bees, hoverflies and butterflies. Butterflies in numbers in October, with a species diversity that would rival the height of an English summer.

This should hardly be surprising. Prince George’s County in Maryland has a butterfly list of over 100 species, despite covering an area almost exactly the same size as Berkshire. This lepidopteran exuberance is partly due to the geographical layout of North America – the position of Maryland mid-continent means that many migrant species of butterfly can reach it from the Deep South, via a relatively straightforward overland route. I believe several of the species pictured here are migrants. It’s also due to the steady supply of heat into the climate. As discussed on a 58-comment evolution megathread on the Biolist 2012 Facebook group last week, the more southerly position of the Americas compared to Europe means it is also warmer on average. This means higher heat energy input to natural ecosystems, which tends to result in greater biological diversity.

Regardless of how or why I was surrounded by butterflies in early October, they were a marvelous consolation for an occasional lack of action on the bird front. I’d either never seen or never noticed some of these beauties before: variegated fritillary, eastern tailed-blue, whirlabout, grey hairstreak, pearl crescent. And even away from butterfly hotspots like that lunchtime at Governor’s Bridge, there’s the joy of seeing an orange-tinged leaf glide past only to have it flap before your eyes, revealing a dark, spotted body powering magnificent wings for mile after mile: the last monarchs are still passing on their way to Mexico.

Over this past weekend the weather gods played another trick card from their hand, and answered my plea for more seasonal conditions by sending temperatures plummeting: a dank, pervasive, all-too-English-style cold accompanied by stinging squalls of rain. Thanks for that. But now, at last, as I write the temperature is back to where I would expect it to be, and the skies are mostly blue, littered with pleasingly puffy clouds. I hope a few of the migrant birds might be out at the same time as I am for the rest of this week, enjoying such clement conditions. During the hot spell I should have been out at sunrise to catch up with them whilst still active. As if that was likely to happen. During the cold spell, which we spent visiting up in Pennsylvania, migrants were mostly missing in action, presumably falling out ahead of the cold front where habitat was better, i.e. back in the more heavily wooded areas here in Maryland. I can’t wait to get out and see if any are still out there.

Photos from top to bottom: Variegated fritillary, whirlabout, pearl crescent, eastern tailed-blue.

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