The Carolina Wren
Project FeederWatch gets a bird's-eye view
The Carolina Wren is best known for its surprisingly variable and much-studied vocal range. But Project FeederWatch (PFW) has its eye on the Carolina Wren's equally interesting geographic range as populations expand into the northeastern United States. Severe winters can set back expansions temporarily by killing large numbers of wrens, but mild winters for the past 20 years have assisted the wren's efforts in moving northward.
Traditionally, Carolina Wrens inhabit the warm, southerly regions of North America. A quick glance at the 1995 PFW geographic range map (page 7) shows where Carolina Wren populations pack the southeastern United States. With healthy populations in southern territories, wrens may be searching for, and finding, new places to call home. FeederWatchers now report the Carolina Wren flitting about as far north as New York State and Michigan.
FeederWatcher Nancy Hammond of East Lansing, Michigan, stated in her 1996-97 Rare Bird Form, "This is my first sighting of this bird here in over 25 year's residence." As the PFW range map indicates, Thryothorus ludovicianus, the Carolina Wren, has established its territory far into Michigan, which is well known for its hard winters.
Nonmigratory birds, wrens establish winter territories; they also form pair bonds--or mate--for life. Maintaining a winter territory means wrens do not leave established areas when temperatures drop below zero. Severe winters can kill this wren, primarily because it usually forages for food on ground that's not covered with snow. An insect eater, it prefers spiders and bugs. But FeederWatchers report that Carolina Wrens will eat high-fat suet and black-oil sunflower seeds at feeders. The PFW data (see graph, page 7) from the BirdSource web site http://www.birds.cornell.edu/pfwtrends/ show the percentage of FeederWatchers who reported seeing them in the Northeast FeederWatch region.
New FeederWatcher and long-time birder John Greenly of Lansing, New York, supports these findings. "I've witnessed Carolina Wrens breeding and wintering here every year for the last seven years." He has rarely seen Carolina Wrens at his feeders. Most likely they'll be at the edge of the woods, "foraging near the ground, seeking bare spots when it's snowy." He thinks that sunflower seeds and suet, which he puts out to attract other species, "may improve the wrens' survival during tough times."
Continentwide, from the middle of November to the middle of April, nearly 13,000 Feeder-Watchers observe birds while recording data on various species, weather conditions, and food used during the winter season. Feeder- Watchers then send their data forms to the Lab. These forms are used to update findings such as those on Carolina Wren population changes.
Diane Tessaglia-Hymes, research coordinator for PFW, is excited about tracking Carolina Wren population changes throughout the species' range. She says that changes in the wren's expansion and reduction are cyclical and believes that warmer weather locally, possibly related toEl Niņo, could cause wren populations to rise in the coming year. "I predict that the percentage of feeders visited, which may be an indicator of the population as a whole, will probably go up because this winter has been mild," said Tessaglia-Hymes. She notes that Carolina Wrens are resident birds maintaining winter territories; thus, wrens surviving the winter will probably attempt to reproduce in the spring. Her prediction is based on PFW data collected over the past 10 years.
FeederWatchers submit anecdotes about birds they see, too. Participant reports such as Nancy Hammond's (East Lansing, Michigan) Carolina Wren sighting help PFW stay in tune with species' movements into uncommon territories. Project FeederWatch education coordinator, Margaret Barker, often talks with Feeder- Watchers. "Part of my job is to keep in touch and interact with FeederWatchers all over the country. It's very exciting to see how PFW is used--not only to further bird research, but to promote education about birds. Participating in PFW allows people to learn about bird research, science, and the scientific method. And, they learn how scientists think."
FeederWatcher input is proving invaluable to bird research, as shown by studies such as Carolina Wren population trends. Says Barker, "Your observations are so important. Every piece of data helps tell the story of North American feeder birds."