Birds : Stories of spring
The pace of migration, both the diversity and volume, quickens significantly in the middle of April. The waters surrounding Martha's Vineyard are an avian highway and on shore, birds are hard to miss. New land birds arrive almost daily as others depart. It is a very exciting time of year for those of us interested in birds.
Average temperatures have been gradually increasing as the days keep getting longer as well. This is a subtle time of the year and while change is happening all around us, it is often hard to see. While the weather has been typical of a Vineyard spring, up and down but mostly cold and damp, for birds, serious business is at hand. That is the job of perpetuating their respective species. Most resident birds are already paired off and either laying eggs or incubating.
Photo by E. Vernon Laux
Evidence of the breeding season is hard to miss. Many osprey pairs are engaged producing eggs or have recently completed clutches. An average clutch of eggs for osprey is three, but they vary from two to four eggs. Like most birds of prey, but unlike most songbirds, ospreys begin incubating the moment the first egg is laid.
This means that the first egg hatches earlier, in some cases three or more days before the second chick emerges. The first chick to hatch has a big advantage over its younger siblings. This survival strategy for raising young has evolved to benefit the species. In years with good weather and lots of food, two and rarely all three chicks survive. Often this is not the case and only one chick makes it to fledging. This is nature's way. Osprey eggs hatch after 32 or 33 days of incubation.
The migration seems to move in fits and starts, especially for land birds. The Head of the Lagoon was crowded with fishermen in search of trout this past week. Most were unaware of the four black-crowned night herons, the ring-necked ducks, a dozen bufflehead, and numerous yellow-rumped warblers and white-throated sparrows that were active and singing as well. This location is one of the best spots to witness the spring land bird migration on Martha's Vineyard and has produced many memorable birds and days in past spring birding.
The first two weeks of April have provided lots of excitement in the form of southern birds flown too far north. Birds that nest well to the south of Martha's Vineyard migrate earlier in the spring than birds nesting further north. Occasionally as they rush back to breeding grounds they get caught up in the strong frontal systems that have been particularly active this spring and travel further than they had planned. Birds in this category already this spring include two prothonotary warblers, and two blue grosbeaks species that nest as far north as southern New Jersey. Other early arrivals include a parula warbler on March 30 in Oak Bluffs and an indigo bunting on April 2 on Chappaquiddick.