Field Observation #3

This morning (Saturday, March 18th) at around 9:30 I drove out to Fannie Stebbins Memorial Wildlife Refuge. It was a chilly morning - around 30 degrees - but clear and sunny. I grew up driving through this area with my dad on saturday mornings, and knew I would see many familiar faces. When I arrived, there were about a dozen other people out birding; by the time I left, that number had doubled. Because many birders bring food along with their binoculars and telephoto lenses, the behavior of the birds was strongly affected by our presence even before I started pishing.
The first thing I noticed when I left my car was that there was an absolute symphony of calls; in my last two excursions, weather has been suboptimal. Today was completely different, and the abundance of birds seemed a testament to that. I could immediately pick out more than half a dozen species, the most prominent of which was the Red-Winged Blackbird. It seemed as though everywhere I looked I could spot a vibrant red and yellow shoulder badge. These birds did not respond favorably to my pishing, and as soon as I started they began to fly away and vocalize alarm calls. However, it did summon a curious Black-capped Chickadee and elicit alarm calls (without flight) from a Blue Jay and a Northern Cardinal. I think the pish is meant to sound like a distress call, although mine definitely left a bit to be desired.
In addition to seeing how the birds interacted with me, I also witnessed many inter- and intra-specific bird interactions. I watched a group of Canada Geese attempt to steal food from a gull. They postured and honked, spreading their wings, stretching their necks, and following the gull. Oddly enough, the gull didn't give up his prize; he just kept walking away with the food, and after about 15 feet the Canada Geese gave up and turned around. The local birders apparently keep them well-fed enough that it wasn't worth any more bullying than that! I also noticed a dramatic lack of territoriality in another species; I saw 5 male Northern Cardinals eating from the same pile of bird seed, all within about a 6 foot radius. It struck me that the birders' behavior (of spreading seed and exponentially increasing food quality/forage density) is almost certainly shifting birds' social behaviors in areas like this refuge. However, the group foraging behavior is economic in this instance, and phenologically speaking it's likely too early for competition for mates to be high enough to warrant energy-intensive territoriality.
The striking red plumage of the male Northern Cardinals stood in stark contrast to the white snow and blue sky; it also stood in contrast to many other species that I saw. Song sparrows seemed to blend into the background, their neutral brown stripes blending in perfectly with stems and branches. Mourning Doves' soft beiges blurred against the sandy soil and the leaf litter covering the ground. In contrast, the male Northern Cardinals were displaying vibrant plumage that's likely more influenced by sexual selection than by predation on an evolutionary timescale.

Publicado el 18 de marzo de 2017 a las 08:16 PM por cafrigo