Tuesday, July 21, 2009

Babes in the Woods

Northern Mockingbird. Photo by Doug Brown

Just another day in field, this time near the end of the nesting season. My expectations were low, particularly because this area had been mechanically cleared, leaving either an open, weedy field, or a cottonwood forest mostly devoid of understory vegetation. That, combined with the weariness that results from too many very early mornings, and the impending July heat and humidity, left me dreading the next three hours it would take to complete the survey. I trudged out to the start point, dutifully arriving before sunrise and, looking to the east, visually confirmed that this would be yet another futile exercise in negative data collection.

But, as I slowly traversed the transect line, my ears thrilled to the calls of birds that make a living on the edge: forest edge, meadow edge, and the interface that connects them. The first surprise was the call of a bird I’d never before heard at this site, a Northern Mockingbird. And, it sounded none too pleased. Scanning with my binoculars, I found the bird with a large bug firmly clamped in its bill calling for its fledgling. The youngster quickly responded, getting a bit of breakfast, and then diving into the shrubs nearby. Suddenly, Mom (or Pop) took offense at the presence of another bird, shrieking a warning and taking chase. Each time the hapless intruder tried to land, the mockingbird dove on it, shrieking a warning. They moved, snag to snag, tree to shrub, as Mom harassed the other, as yet unidentifiable, bird until it moved beyond the invisible line that formed the mockingbird’s territory, the area it had claimed for its own family.

My curiosity aroused by the scuffle, I scanned for the loser of the battle. It was an American Kestrel, the smallest North American falcon and normally not a threat to a mockingbird which is almost the same size. However, this falcon also was a fledgling, one of three young that the kestrel parents had produced. Although certainly no threat to the mockingbirds, the little falcon was getting a lesson in territory boundaries, not to be crossed with impunity. Each time the little falcon landed, the mockingbird stooped and the falcon ducked, before taking off for a safer perch. Soon it was joined by its siblings and the three nosily flew from tree to tree, practicing takeoffs, turns, dives, and precarious landings. Carefree, with no worries, but with new knowledge of the invisible territory fence to the south, these kestrels were unaware of all other dangers, and secure in their assumption that food would be forthcoming via their parents indefinitely.

Before I moved beyond the kestrel family, however, Mom coyote took exception to my presence in her territory. She howled; she barked; she warned. Now, I had intruded beyond her invisible territory line, and was a potential threat to her babies, who also were out of their den and beginning to explore their new world. She stayed with me, always out of sight behind a shrub, incessantly barking. Mentally, I tried to let her know that I bore her family no ill will and that I would soon pass by. My silent message, “Please stop! I mean you no harm, and I can’t hear any bird calls with all this racket.” It did no good. She kept up her noisy vigil until I passed beyond the boundary line on the other side of the territory.

Moving into the woods, my first sight was of Dad Cooper’s Hawk carrying prey toward the nest, pursued by three noisy, begging fledglings. Although I couldn’t see the nest antics as the youngsters squabbled for food, it was easy to envision the action. One baby hawk secured the prize while the other two loudly expressed their displeasure, moving to nearby perches and resuming their endless whiny, begging calls. At this time in their lives, their food demands are so great that it takes the combined efforts of both parents to hunt for enough prey to satisfy their offspring. (Cooper’s Hawks are primarily bird-eating hawks and it takes an average of 67 robin-sized birds to successfully rear a single young). Eventually, the din subsided as the hawk babies turned their attention to exploring their new, forested world, and I resumed counting birds.

As I began to near the forest edge, however, a fierce ‘killy-killying’ broke through the otherwise peaceful reverie of compatible bird calls. Killy! Killy! KILLY! Clearly, the kestrel family was on the attack, and based on the decibel levels, it was a substantial effort to eject a perceived threat. It wasn’t until I cleared the forest edge that I was able to see the source of their distress, a fledgling Cooper’s Hawk that had dared to fly beyond its forest territory and had perched in a branch on the edge of the opening. Coops are mortal enemies of kestrels who are just about the right size for prey. However, baby Coop had no idea yet, that he/she would ever had to hunt for food. He also was unaware that .
his territory ended at the edge of the forest. There the little hawk sat, with the supreme confidence of a toddler, completely exposed in a foreign land. Clearly, he had a few lessons left to learn.

Mortality rates in the avian world run high. About 7 of every 10 youngsters do not survive to one year. Although they are biologically equipped with survival tools, hunting, flight, and a healthy fear of humans are learned skills. As I watch the young of the year bumble along, the avian equivalent of toddlers-on-the-loose, I am amazed that any of them survive. The ones that do, learn their lessons quickly for, in the wild, a single mistake might be the last one they ever make.