Crow hunting was not regulated in the United States until 1972, the same year that DDT was banned. Merlins do not build their own nests and usually take over abandoned crows’ nests, but until recently, crows have been unwelcome in areas of human settlement. If small prey items were more common in cities in past decades, why have Merlins only recently moved into urban areas? The most likely explanation is that there has been a dramatic change in human-crow relations over the last thirty years. It is worth noting, however, that the availability of small birds in urban areas has not increased appreciably in recent years if anything, it has declined. The city-born birds were much less likely to migrate than others.
In the 1970s, Merlins began appearing in cities on the Canadian prairies, apparently attracted by high numbers of Bohemian Waxwings which, in winter, feed from ornamental fruit trees. Merlins are tolerant of people, able to thrive in many different habitats, and feed on birds that commonly live near human habitation. Scientists have a better idea of why these birds have chosen to breed and winter in cities. Bird behavior is far more malleable than most people suspect, and Merlins seem to be a particularly adaptable species. Or perhaps a few pioneering birds deviated from their usual migratory route and found that the boreal forests of the Adirondacks were suitable habitat. It may be that, for whatever reason, the Merlin population in the north has grown, forcing individuals to colonize new territory further south. There is no obvious answer for why Merlins have dispersed so widely around the state. Yet this still does not explain why there seem to be more Merlins now than ever before. When these chemicals were banned, Merlin populations rebounded. In the nineteenth century, Merlins declined in some parts of their range due to persecution later, their numbers were again seriously reduced by the widespread use of organochlorine pesticides, including DDT. However, because the Merlin catches small songbirds on the wing and so prefers more open habitats, it is not clear that reforestation has been to its benefit.
The landscape of New York has transformed dramatically in the past hundred years as cultivated land has reverted back to forest, a change that has benefited many species. Global climate change is pushing the ranges of many birds northward, but the range of the Merlin is expanding south, against the trend. The reason for this dramatic shift in range is not yet clear. They now both breed and winter in almost every corner of the state, from Rochester in the north to Buffalo in the west and Binghamton in the south, and have become increasingly common in urban areas.
The birds established themselves in the park very quickly and, from there, spread to the rest of upstate. Scientists were therefore surprised when breeding Merlins were sighted in the Adirondacks in the 1980s. There is no evidence that Merlins were ever any more than occasional visitors to New York State, which is situated on the migration route between their historical breeding grounds in Canada and their wintering grounds in the tropics. Merlins are a circumpolar species, inhabiting the prairies and boreal forests of the higher latitudes of both Eurasia and North America.
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