Blog #371 The Great Race
Early arriving red-winged blackbirds foraging for food, courtesy of Jerry Acton.
Spring, that cold, wet joke played on us in the Finger Lakes, technically begins in three weeks—March
20. Despite the wintry weather, birders have already checked off several “spring can’t be far away” migration milestones like killdeer, red-winged blackbirds, and turkey vultures. But for me, no early spring arrival is more awaited and anticipated than the first of the Osprey. Reports of Ospreys in January, February, and early March are usually clouded by hope. Few if any good records of Osprey in the Finger Lakes exist in these months and these invariably turn out to be red-tailed hawks, great black-backed gulls, and immature bald eagles.
Woodcocks huddling in the snow, courtesy of flicker.
Migrating Osprey heading north past the Chesapeake Bay, courtesy of Mike Maguire.
In early spring, the great race begins—spring migration’s land-grab. The first birds to arrive on their breeding grounds get first choice of nesting sites and the best resources, but they also risk arriving before food is available. First arrival dates of Ospreys breeding on Cayuga Lake have been erratically advancing
Ospreys reuniting at their nest in Lansing.
over the last decade starting from April 5 to the last two weeks of March. Is this a result of a warming climate? According to Horton et al. (2019) and the United States Geological Survey, rising temperatures are causing birds at temperate latitudes to migrate earlier each spring. Since 1971, the average journey home is advancing by about 2–2.5 days each decade, varying with different species. With Ospreys, the annual advances are more noticeable, advancing a few days each year. What is unsure is how these phenological events will change over longer time frames.
The phenology or annual cycle of molt, breeding, and migration of Ospreys breeding in coastal southern New England, which start breeding earlier than Ospreys on inland lakes. Thick lines show peak activity and thin lines show off-peak. Phenology varies with location. Diagram courtesy of Birds of the World.
Phenology is the schedule of annual plant and animal cycles driven by the climate and is highly vulnerable to sudden changes. Plants and animals adjust the timing of certain phenological events, such as tree budding, flowering, or migrations correlated with the climate. Synchronization of these cycles is imperative for the world’s ecological systems to function. A changing climate threatens this organization. For example, plants may bloom before butterflies emerge to pollinate them, or caterpillars may emerge before migratory birds arrive to feed them to their young. As the climate continues to change plant and animal species must adjust to the associated increase in unseasonal temperatures, drought, and extreme storms. These perturbations interrupt the normal interspecies interactions and the overall functioning of ecosystems.
According to Osprey expert Alan Poole, “Ospreys start to appear in late March when winter and spring vie for dominance... Ospreys seem to materialize magically on such warmer days...” Typically, already mated males, highly motivated to defend their nests, arrive just before the females. If the males find their nest occupied by a goose or an eagle, they will fight to drive off these larger usurpers. Such fights waste valuable time and energy and can be life-threatening, but maintaining ownership of a nest is paramount— without a nest, there is no next generation. Once the breeding pair reunites, courtship commences and the breeding season starts.
Getting an early start on the breeding season gives the offspring a huge advantage over young birds born later. The earlier the reunion of the breeding pair, the earlier eggs are laid and young are hatched. Early nesting gives the young of the year the advantage of time—and time is everything when it comes to
survival. A few extra weeks to learn and perfect the critical skills of flying and foraging could make all the difference in these birds’ lives, enabling them to survive their first solo migration south and thrive during their first years.
Female Osprey arriving at her nest, courtesy of Bob Howdeshell.
Unmated birds arrive at the breeding grounds after established pairs have claimed their nests. They roam the area searching for possible nest sites and nests with missing partners. Two-year-old Ospreys return to their breeding grounds for the first time about a month after the older birds. They are not as competitive for nests as older, established pairs and have no reason to rush. Once home, they search for places to nest, and, if one is found, a male will start building in hopes of attracting a mate. However, more often than not they are unable to secure a nest until they are older and more seasoned. Another year of maturation will enable them to migrate sooner and be more competitive with older birds for nests.
The evidence is clear that the changing climate is causing a gradual shift in one of nature’s grandest natural phenomena—bird migrations. If this happens faster than other components of the ecosystem can adapt, the elegant ecological synchrony of biological systems collapse. Lessons from the DDT crisis have taught us to take heed of the Ospreys’ warnings. Are they already warning us that something is wrong with the environmental clock?
Candace
Candace E. Cornell
Friends of Salt Point Natural Area Cayuga Lake Osprey Network Lansing, NY
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