June 29 vulture chicks
June 29 vulture chicks
Last year I wrote a column on turkey vultures and my unsuccessful attempts to confirm Maine-nesting vultures as part of the statewide five-year Maine Bird Atlas project. I’m glad to report that 2019 nesting-season statistics had a major turnaround when a local landowner informed me of a perennial nesting site on her property. On May 12, I visited the secluded wooded grove and then made follow-up surveys most every week through the summer. I strove to keep these sessions brief to limit stress on the developing nestlings and parent birds.

The nest itself was housed in a complex of ledged rock formations divided by a narrow cleft that permitted access to the grotto entrance. Two sizeable eggs — creamy white with brown spots and splotches — lay side by side on a blanket of bare oak leaves. A moss-covered shelf of overhanging granite provided shade and protection from the elements. Within such cave environments, tropical summer temperatures are generally 11 to 13 degrees lower than ambient temperatures outside.

For such bulky individuals, vultures are rather timid and secretive by nature. They do not build a nest as such. Instead, cave and cliff banks, hollow stumps, dense shrubbery and old buildings are commonly utilized. Careful concealment from predators is essential due to strong odor when young are being fed. By contrast, many nest-building birds transport materials with their bill (most songbirds) or feet (raptors). Vultures fit neither transit category since their large feet are relatively weak and vulture bills aren’t well suited to these tasks.

Incubation of eggs takes between 30 and 45 days, with both parents sharing the responsibilities. When I returned there on June 22, two white downy chicks were huddled beneath the shield of rock. They were practically immobile at that early stage, but each puffed its feathers and lifted its stubby wings to appear bigger and more intimidating. The chicks opened their bills and hissed defensively. Lacking a syrinx, the muscular song-producing organ of songbirds, vultures only hiss and make grunting sounds.

In between my regular weekly checks, the chicks grew rapidly. By June 29, dark pin feathers had emerged along the wing margins. By the July 15 visit, their ever-lengthening wings were sheathed with blackish covert feathers, still framed by white down. New feathers do not develop randomly; they grow in specific patterns or rows called feather tracts, like penciling in a trace-the-dots design puzzle. And a full set of flight feathers was evident on July 20.

July 27 was a red-letter day for a couple of reasons. The chicks were now demonstrating signs of independence from the tight confines of the grotto. Upon my arrival, they stood in unison atop the rock ledge overlooking the nest. Clad with black feathered backs, they had also grown a half-length set of tail feathers.

Something else was markedly different on this occasion. For the first time during our brief acquaintanceship, the vultures did not hiss at me. They eyed me with wise caution, but remained silent. I speculated about their change of behavior. In consideration of our multiple face-to-face contacts, had the pair grown acclimated to seeing me? That same guy who appeared once in a while, peering down into their inner sanctum. That fellow who didn’t stay very long, didn’t harm or threaten them, and quietly left the premises shortly thereafter. An acquired sense of familiarity? Perhaps so, but there was possibly more to it. On previous visits, I’d stationed myself above them to shoot interior photos. Now their own elevated position on the ledge top placed them safely above me. They never hissed at me again. More in my next column.