In warm climates it is a common complaint that the season of sunshine, sweaty brows, and high electricity bills seems to set in earlier and earlier each year. A new study suggest that the old adage that March “comes in like a lion and out like a lamb” might one day be applied to February instead, that is, according to the nesting birds of springtime.
A recent study published in the British Ecological Society’s Journal of Animal Ecology suggests that, when compared with historical nesting data, a significant number of American birds across various species are nesting earlier in the year. The study, which looked at nest data from historical collections in several Chicago area museums, found that eggs collected between 1880 and 1920 were laid up to an entire month later in the season than the modern descendants of the birds included in the study.
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Victorian Nesting Season
Egg collecting is a forgotten hobby which was most popular during the late nineteenth and early twentieth century. Collectors were often gentlemen who would go to great lengths to retrieve intact eggs from nests. One enthusiast is even reported to have collected an egg whilst taking enemy fire, smuggled it to safety within his own mouth, and removed one of his teeth to free it when he found that he could not spit it out intact.
This somewhat unusual hobby is an incredibly valuable source of ecological data. Egg collectors, out of meticulous care in some cases and doubt over egg identification in others, often wrote detailed accounts of the nest locations, conditions, and dates of their finds. These are maintained in museum collections now and provide crucial data regarding the ecology of birds a century ago, and the way that bird reproduction has changed.
Between the historical samples taken over a century ago and the nesting habits observed today, as many as seventy-two species of birds, including blue jays, chickadees, various birds of prey, and many migrant and resident species, have advanced their breeding season by a maximum of fifty days and an average of about twenty-five days. This is shocking, perhaps, but not entirely surprising. Existing studies have already noted that over the last forty years or so the onset of spring weather has shifted to begin as early as eighteen days ahead of its historical schedule.
This affects all parts of nature. When plants begin to grow early, the insects that sustain themselves off of these plants begin to appear. The insects bring in the birds and animals which feed on them. This is just one model of the change that is being observed. Earlier fruiting seasons for trees also affects the seasonal behaviors of birds.
Nesting Birds and Climate Change
The study also proposes a possible cause for this advancement of the nesting season. According to the study, earlier nesting seasons can be observed to follow a trend of rising carbon dioxide levels. Thus, climate changes are the likely culprit for this phenomenon.
While birds nesting earlier than usual may not be inherently harmful, it is being looked at by some ecologists as a possible red flag indicating the enormity of humanity’s impact on birds, their behaviors, and their populations. Additionally, while warm weather is tending to set in earlier and earlier, these early springs are often volatile and may feature sudden drops in temperature which may endanger early birds’ nests.
Over the last fifty years an estimated loss of over three billion birds has occurred due to a variety of causes both known and unknown. This is a devastating blow to earth’s ecosystem and suggests that studies like the one from the Journal of Animal Ecology are more important than ever. It is essential that we identify threats to bird populations and do whatever possible to preserve avian ecosystems.
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