Specialist to speak on ravens

HOLDEN – Perhaps no other bird has captivated the human imagination as has the raven. Big, black and loquacious, the raven commands attention. Ancient folklore across cultures affirms this eternal fascination with the raven, seen by some as a talisman and by others as a scourge.

American Indians revered the raven because it led them to game. Their raven appears as god and trickster in legends, bestowing light on the world. Yet he is not above plaguing humans with mosquitoes for his own amusement. In contrast, in Old World literature, “the slaughter-greedy” raven portends death. It haunts battlefields and casts ominous shadows over houses infected by the plague.

Though steeped in lore, the raven remains enigmatic from a scientific standpoint. Unlike the gregarious crow, whose numbers have increased as humans have spread out, the raven has been threatened by human settlement. Intelligent, wily, wary and wide-ranging, it can be a tricky subject of objective study.

Danielle D’Auria, a wildlife biologist for the Maine Department of Inland Fisheries and Wildlife, will give a talk on ravens at 7:30 p.m. Thursday, Oct. 19, at Fields Pond Audubon Center.

As a graduate student in the wildlife science department at New Mexico State University at Las Crusas, D’Auria spent two years studying the Chihuahuan raven. Smaller and more specialized than the common raven that resides here in the Northeast, the Chihuahuan raven proved to be every bit as intelligent and interesting to observe.

According to D’Auria, “Even though the Chihuahuan raven is abundant, it is a ‘neglected species’ in the sense that there are some basic aspects of its breeding biology that are missing from the literature.” D’Auria studied both breeding biology and social behavior of the Chihuahuan raven. In particular, she examined how the relative abundance of grasshoppers, a nestling’s primary food source, influenced the survival rate of the young.

D’Auria also studied social behavior surrounding nesting to see if the Chihuahuan raven engages in cooperative breeding, wherein yearlings help raise the next year’s nestlings by bringing food and defending the nest against predators. The crow is an example of a known cooperative breeder.

“There had been hints in the literature in the past that ravens are possibly cooperative breeders, but I didn’t see any evidence of that,” said D’Auria.

The bird’s intelligence sometimes impedes research. D’Auria explained,

“For example, I wanted to mark as many birds as possible so that during my observations each bird would have a unique identifier, but I found that capturing them was much more difficult than I had expected. They learn quickly,” she said. “In the first year, I caught and marked 112 birds. In the second year, I caught and marked 11. Capturing them was probably one of the most challenging aspects of the study, because they’re such intelligent birds.”

D’Auria tried a number of methods, including the Australian crow trap, a large 8-foot-by-8-foot cage with a horizontal ladder as part of the roof. The narrow openings between the ladder rungs allow birds to fly in through the top but, at least theoretically, prevent them from flying back out.

“The idea is that the birds can swoop in to retrieve the bait, but to get out they would have to spread their wings to fly up,” D’Auria said. She captured some birds that way, but observed some birds outwitting the trap. The jail-breakers would swoop down from an upper corner of the cage, turn upward quickly, tuck their wings and escape. Once caught, most ravens knew to avoid the trap a second time.

At times D’Auria felt like the specimen under study. Some of the birds soon learned to recognize her truck and would become skittish and flush from their nests. Despite her best efforts at camouflaging herself in the desert – a place with limited natural cover – the wary birds sometimes discovered her hiding place and perched above her in the trees as if to see what would happen next.

For directions to Fields Pond Audubon Center, call 989-2591. Admission, which supports the center, is $5 for Audubon members and $6 for others.