John James Audubon spent much of the spring of 1829 searching for and documenting birds along the shores of New Jersey and in the mountains of Pennsylvania. Rather than pay for a room in a pricey inn in Philadelphia, Audubon opted to stay in a modest boarding house in Camden, New Jersey. In addition to saving money, Audubon gained from his second-floor room the perfect vantage point to watch just outside his room window a pair of Warbling flycatchers nesting in a poplar tree. Audubon could also see lurking below a “grimalkin” with its sights set on the nest.
John James Audubon even began to notice that in addition to snakes and other creatures, birds were facing big trouble with pet and feral cats. “Cats that have abandoned the houses to prowl about the fields, in a half wild state, are also dangerous enemies, as they frequently approach the nest unnoticed, and at a pounce secure the mother, or at least destroy the eggs or young, and overturn the nest.” Cats prowling about fields, gardens, yards and all of their other haunts amounts today to more than 2.5 billion birds killed annually.
Once the Warbling flycatcher female started to produce eggs, Audubon noted her laying one egg a day for five straight days. The parents then took turns incubating the eggs for 12 days. Once hatched, the chicks remained in the nest for 15 days. Even though fledged on the 16th day, the young birds moved and perched close together in close proximity to the nest. On the 17th day from when the chicks hatched, there was neither a sign of nor a peep from the Warbling flycatcher family. “Never had [François] Huber [1750-1831] watched the operations of his bees with more intentness than I had employed on this occasion, and I bade them adieu at last with great regret.” The Warbling flycatcher is known today as the Warbling vireo. Audubon added that the Warbling vireo ranged “From Texas to Maine, and in the interior to Columbia river. Abundant. Migratory.” Whether due to cats or other challenges, nowhere in the United States today can the Warbling vireo be considered abundant.