BirdWalk Newsletter

Transcription

1 BirdWalk Newsletter Walk Conducted by Perry Nugent and Ray Swagerty Newsletter Written by Jayne J. Matney Cover Photo by Angie Bridges It s not only fine feathers that make fine birds. Aesop The Jay and the Peacock It has long been a mystery as to how brood parasites-those birds which lay eggs in other species of bird s nest- can effectively have the birds raised by other species and still have their young grow to have their own recognizable behaviors and identify with their own species. Many studies have been done in human biology with twins separated at birth to try to master an understanding of the environment versus genetics realities of nature. Survival of a species is dependent on the individuals to thrive and produce offspring. In order to do this, they must be able to fill their specific niche in the world- eat what they are meant to eat, live where they are meant to live, and behave as they

2 are meant to behave. But when a bird is raised by another species in the first stages of life, which is supposed to be such a critical time in the imprinting process, as with these brooding parasites, how do these individuals catch on to who they really are? According to two scientists and colleagues, Mark Hauber and Matthew Louder, the cowbird is a perfect example for studies on this topic. The initial study shows that the young cowbirds are like young human teenagers they sneak out at night to gather with those most like themselves. For these birds, this is a necessity to being a cowbird. But unlike human teenagers, these cowbirds are actually sneaking out to be with their parents! And other cowbirds. It seems that the parents don t actually abandon their offspring. They will keep a watch on Great Blue Heron Pair Photo by Guenter Weber them while the other adoptive parents feed and shelter during the day. Then in the evenings, the young juvenile cowbirds will innately explore into areas such as fields where they are supposed to roost and find other cowbirds.

3 Hawk Eyes Photo by Cathy Padgett This streak of independence early in age along with the innate behavior to roost in fields allows them to come into contact with their own species and families. This also keeps the cowbird juvenile from becoming too close, and therefore imprinted on, to the false behaviors from the nest. Counter experiments have shown laboratory birds, which are not allowed to interact with their own species, are confused and will show signs of adopting the wrong behaviors. Therefore, they use incorrect vocalizations and try to mate with the

4 wrong species of birds. While Hauber s and Louder s studies began showing these unique methods of becoming a true cowbird, another scientist, Kathleen Lynch, was studying the evolution of maternal care in birds. Her area of expertise happened to be the neurological references to behavior. Hauber began hypothesizing that there must be a trigger, a cue, or some password leading these young birds to home-in on the proper individuals (other cowbirds) from which they need to learn from. To fully test this theory, he needed an avian neuroscientist to help. Hauber and Lynch began collaborating to find this password or mechanism which gets triggered for the learning processes of these birds. Once they narrowed it down in their research to an auditory cue called chatter, the two scientists distinguished the two components of the entire auditory Brown Thrasher Chuck Fuhrman

5 processing system for these birds. First, the chatter triggers the brain to identify other cowbirds and focus on those birds. Then secondly, now that the bird has its cue, the bird then learns songs from these cowbirds and cowbird flocks. Fledglings are attracted to the chatter. So, it is a matter of locating others of the same species through the use of the chatter password and then going through the process of learning what they need to learn to become a cowbird. Experiments have shown how critical this two component system is to the proper learning of these birds. Cowbirds have been shown to use canary songs if left with no choice but to listen to canaries. In the wild however, the cowbirds put themselves in situations which ensure them exposure to the proper chatter password as seen in the original studies. According to Gregory Kohn, a behavioral scientist at New Mexico State University, experiments can do a great job identifying species recognition cues, but he believes it is more complex than just one cue. He believes it relies on a diverse range of multisensory cues as the cowbird develops from a nestling to an adult within the flocks. As studies progress, a better understanding of the many cues needed to guide these birds into species recognition will become illuminated for us. Information for this article came from: Gabbatiss, John, Scientists Pinpoint the Secret Password That Unlocks Cowbirds Self-Identity, Audubon, 2017; Soniak, Matt, How Does a Cowbird Learn to be a Cowbird?, Audubon, Turtle Yoga in the Sun Photo by Jo Frkovich

6 As the Yellowrumped Warblers are decreasing in numbers because of migration away from the area, other species such as the Prothonotary Warbler are beginning to increase in numbers for a spring nesting period. The Great Egret nests are increasing in numbers in the Rookery. Prothonotary Warbler Photo by Marc Regnier More Little Blue Heron, and Black-crowned Night Heron are also coming in to begin breeding as well. Wood Duck and Great Blue Heron are still being seen with young- especially in the Ravenswood and Audubon Swamp areas. April 15 th happened to be a warm, humid day. A storm front was moving in and expected in the afternoon/evening. Immediately, in the parking lot, a Downy Woodpecker, Blue Jay, and White-throated Sparrow were the starting birds for the list. Blue-winged Teal, Anhinga, Snowy Egret, Common Moorhen, and Laughing Gull contributed to the count in addition to those previously mentioned. Turkey Vulture and Black Vulture were seen overhead. Redshouldered Hawk and Red-tailed Hawk were seen in the cabin areas and Fernanda s Field location. The Red-tailed Hawk was busy fending off a few crows. Pileated Woodpecker and the Red-bellied Woodpecker were seen and heard scattered about on the property. The Great-crested Flycatcher and the Common Yellowthroat were

7 seen in the Audubon Swamp. Brown Thrasher were located along the oak alley. Finishing off the list were: Mourning Dove, White-eyed Vireo, American and Fish Crow, Carolina Chickadee, Tufted Titmouse, Carolina Wren, Ruby-crowned Kinglet, Blue-gray Gnatcatcher, Eastern Bluebird, Northern Parula, Pine Warbler, Northern Cardinal, Redwinged Blackbird, Common Grackle. Tis the Season for Peacock Feathers Photo by Guenter Weber