We hope these eggs haven’t gone bad in the couple of months we’ve been sitting on them. But a fairly recent study out of Field Museum, via the Journal of Animal Ecology, says the “climate crisis” must be upon us because birds in the American Midwest are laying earlier than they did in Grover Cleveland’s day. And it is a very interesting illustration of how to make a logical omelette. Because when animals are observed not to change their behaviour it's bad because it shows they can’t adapt quickly enough to global warming, but when they do change their behaviour and adapt, it’s bad because, well, because they had to change their behaviour. And if birds are laying earlier it’s also bad, because having a longer warm season for the fledglings to hatch, grow and take wing is obviously bad. Even though we note that in parts of the world where it’s warm all year round there are lots of birds, and in those with a brief chilly summer there aren’t. But what do those bird-brains know?
The press release begins “Spring is in the air” which we, being grouches, would ban along with “‘Tis the season” at a different time of year. But ‘tis always the season for loaded language like “about a third of the bird species nesting in Chicago have moved their egg-laying up by an average of 25 days. And as far as the researchers can tell, the culprit in this shift is climate change.”
Nothing to do with the fact that the metropolitan Chicago population grew from 112,000 in 1860 to 8.9 million in 2021. No, it must be climate change, namely the trend in average Spring and Summer temperatures in Illinois which from 1895 to the present works out to a whole 0.6 degrees C (1 degree F) per century. But to the researcher with a hammer, everything looks like a thermometer. “In addition to illustrating that birds are laying eggs earlier, the researchers looked for a reason why. Given that the climate crisis has dramatically affected so many aspects of biology, the researchers looked to rising temperatures as a potential explanation for the earlier nesting.” Which again assumes that it being warm enough for babies in March instead of April is the chirp of doom.
We do not wish to slight the ingenuity of the study, which begins with the fact that once upon a time, before people were environmentalists, they used to go out and “collect” eggs, meaning snatch them from nests and hollow them out before the little birdies could hatch. It became less fashionable after the 1920s, but in the heyday little regard was given to whether the species was endangered or a living bird would be nicer than a dead egg. But much regard was given to noting what bird laid the doomed egg, where it was collected and when, even on what exact date, and by whom.
In more recent years people again began making detailed studies of what was nesting when and where, they just didn’t kill the babies before they could hatch. But there was quite a pause between the 1880-1920 period of wanton collecting and the 1990-2015 period of data collecting. So a computer model filled the gap, also trying to address differences between Edwardian and modern sampling methods.
It hardly need be said that what happens inside models generally stays inside models. But at least they did worry about things like “outliers”. And “The analyses showed a surprising trend: among the 72 species for which historical and modern data were available in the Chicagoland region, about a third have been nesting earlier and earlier. Among the birds whose nesting habits changed, they were laying their first eggs 25.1 days earlier than they were a hundred years ago.”
Why is it surprising? After all, virtually nobody denies that it’s warmer in Chicago today than it was in 1880. Indeed, the curious thing is that two-thirds of birds did not adapt. But never mind. Because “the scientists hit another snag: there aren’t consistent temperature data for the region going back that far. So, they turned to a proxy for temperature: the amount of carbon dioxide in the atmosphere... We couldn’t find a single source of long-term temperature data for the Midwest, which was surprising, but you can approximate temperature with carbon dioxide levels, which are very well documented,’ says [“curator of birds at the Field Museum and the study’s lead author”, John] Bates.”
So are population records, which go back to 1840 and would make more sense as indicators of habitat changes in an urban area, at least up to 1895 when the official temperature records begin. But we know where the researchers are determined to go. “The changes in temperature are seemingly small, just a few degrees, but these little changes translate to different plants blooming and insects emerging – things that could affect the food available for birds.” Yeah. Like more CO2 promoting plant growth? All of which sounds good not bad if you’re hungry baby bird or parent of same.
Except it’s not. According to Bates, “The birds in our study area, upwards of 150 species, all have different evolutionary histories and different breeding biology so it’s all about the details. These changes in nesting dates might result in them competing for food and resources in a way that they didn’t used to.”
Well, sure. It might. But a greater abundance of food and resources (if food isn’t a “resource”), is far more likely to reduce competition. If you want to go somewhere there’s going to be a tooth-and-claw fight over scarce food, nesting material and anything else except a hungry polar bear looming over you, we again recommend the Arctic.
The basic story here is that life is better for birds thanks to CO2. But the study spins it as death in a shell. As you’d expect.