 |
|
|||||||||||||||||
Project FeederWatch
FeederWatch comes of age in its second decade. Project FeederWatch is about to turn 12, and that's exciting--not only because of the bright future that lies ahead on the Internet but because of the bountiful information collected in the past by FeederWatchers. We now have more than a decade’s worth of backyard bird observations in our databases. Although that may seem like a long time, we are really just scratching the surface of FeederWatch’s potential--we now have barely enough information to discover whether long-term changes exist in the abundance of birds coming to feeders in North America. In the second half of this report, we illustrate how FeederWatch data can be used to explain the yearly variation in the numbers of birds you see visiting your feeders. Data are one of FeederWatch’s legacies; crates of paper are another. After FeederWatchers fill out their paper forms and mail them to the Lab of Ornithology, many things happen: the forms are examined for marks that could confuse our optical scanner, the pages are run through the scanner, comments are read, rare bird reports are examined, and any write-in species are entered into the database by hand. In fact, we are still manually processing the end of last year’s data as we write this summary. Our problem is that FeederWatchers send in a lot of data--but that’s the sort of problem we enjoy. Still, we want to process our data faster, so we can speed up our analyses and tell you what your combined data say about the birds wintering in your area. We also want to make FeederWatchers "citizen scientists" in every sense, by enabling people to examine and analyze the data collected each year. We hope to accomplish both of these goals through our web site at http://www.birdsource.org. To date, approximately 16 percent of FeederWatchers have entered data via the Internet, and we’re hoping that more of you will join the ranks of online FeederWatchers this coming season. Still in the works are plans that will actually enable participants to analyze FeederWatch data themselves, something you’ll be hearing a lot more about when these plans come to fruition. Although the Internet will certainly be the primary way to submit data in the future, we realize that not everyone will be able to report their sightings this way. Every single FeederWatcher is important to us: the greater the amount of data we can amass, the more effective Project FeederWatch will be for detecting and monitoring changes in bird populations. So, if you don’t have access to a computer and the Internet at home, at school, or at a library, please keep sending your paper data forms. El Niņo Just when you thought you were safe from all of the media hype about last winter’s El Niņo, it’s time to find out the FeederWatch angle on last winter’s weather. Using our data, we can answer many questions regarding El Niņo’s effects on birds. As a sample, we will examine whether the unusually wet conditions on the West Coast affected the numbers of birds that visited California FeederWatchers last winter. Although rain was
a major preoccupation for humans in California, FeederWatchers reported essentially the
same numbers of birds as they had in previous years. Warmer-than-normal temperatures in the Midwest and rain in California last winter weren’t the only effects of El Niņo. The major ice storm around the St. Lawrence River in the Northeast last winter could be blamed on El Niņo (what couldn’t?), and this past summer was extremely hot and dry in the southeastern United States. Did these severe weather events affect the resident birds in these regions? We hope Feeder- Watch data will help answer these questions. We will compare this coming year’s FeederWatch data with data from previous years, looking for evidence that the ice storm or the drought affected the number of birds that visit feeders in these regions.
Invasion ‘98: Finches From the North One facet of basic biology currently under investigation by Lab scientists is how wintering birds move across the continent. Last winter’s invasion of northern finches and Red-breasted Nuthatches (see Figure 2) suggests that winter weather is not the only factor that affects when birds move. These winter invaders moved south despite the fact that their northern nesting areas generally experienced warmer-than-average temperatures. See the animated maps tracking last winter’s invasion month by month on our web site at http://birds.cornell.edu/winfin/WFIndIntro.htm.
Invasions of nonbreeding birds are common and have been recorded in Europe as long ago as the Middle Ages. In spite of this knowledge that some species of birds travel great distances during some winters, scientists know very little about what causes these invasions. Because these invasions occur across extensive land masses, even describing where invading birds come from or go to is difficult. Nevertheless, FeederWatch is an ideal source of information, enabling us to look at the movements of invading species across the width of an entire continent. Data from FeederWatch show that invasions are not random events. Figure 3a shows how the abundance of some invading winter finches has changed from year to year. All species in Figure 3a are considered invasive winter migrants, and all are seen by many FeederWatchers roughly every second year. Even more interesting, these species usually travel south from their northern nesting areas during the same years. The simultaneous appearance of several species suggests that a single event is probably the underlying cause of all of the species’ departures from their northern nesting areas in alternate years. Researchers believe that low food supplies farther north cause invading species to travel south. But the invasive species in Figure 3 do not all eat the same foods. Redpolls depend on birch seeds in winter, Red-breasted Nuthatches eat seeds from spruce and fir trees, Evening Grosbeaks feed on seeds from trees including maples and elms, and Pine Grosbeaks prefer to eat soft fruits in winter. Thus, data collected by FeederWatchers suggest that many different types of plants in the boreal forest synchronously produce low numbers of seeds and do so every other year.
Making this hypothesis is easy--testing it isn’t as simple. Unfortunately, seed production is not measured as systematically as bird abundance. Still, scientists at the University of Colorado published a paper (Bock and Lepthien. 1976. Synchronous Eruptions of Boreal Seed-eating Birds. American Naturalist 110: 559--571) in which they gathered the available information on seed production and compared this information with data from Christmas Bird Counts. Their study showed that birch and conifers did indeed produce few seeds every other year and that poor seed production was related to invasive migration. Life would be boring if everything were predictable, and the "every other year" rule has its exceptions. Even though conifers seem to produce abundant seeds only every second year, two conifer specialists, White-winged and Red crossbills, do not stage invasions in alternate years (see Figure 3b above). Last winter was exceptional because both the regular, biennial invaders (Figure 3a) and the less predictable crossbills traveled south together. But why should White-winged Crossbills be so unpredictable? Perhaps you already answered this question when you thought back to last winter and asked, "What invasion?" Although an amazing amount of synchrony exists in the southward movement of several FeederWatch species, not all FeederWatchers saw the invasion. For example, while the eastern half of the continent was seeing last winter’s invasion of Red-breasted Nuthatches, FeederWatchers on the West Coast were recording a sharp decline in nuthatch abundance relative to the previous year (see Figure 4). The same pattern occurred with Red Crossbills. If both eastern and western invasions are the result of low food supply, we should hypothesize that conifers in different parts of the continent are not producing low numbers of seeds during the same years. That would mean crossbills could travel across the continent, north to south, east to west, and winter near a good cone crop. Unfortunately, FeederWatch cannot tell us whether crossbills actually do travel across the continent unpredictably, following sources of abundant food. Nevertheless, science is as much a matter of asking questions as answering questions, so even "negative" data from FeederWatchers are very useful when studying seemingly erratic winter migrants such as crossbills.
Regional
Top 10: Although it’s exciting to find a rare bird at your feeder, even the most common species illustrate interesting facts about North America’s birds and their environments. Which species are common only in a small part of North America, and where are most of these unique species found? From one year to the next, can you easily predict what your most common feeder birds will be? Does predictability vary between different regions of North America? Answering these questions sheds interesting light on the biology of common FeederWatch birds. It may seem strange to think about your common feeder birds as a potential conservation concern. But if your region contains a bird species that is not common anywhere else, that species’ survival probably depends on continually finding good wintering areas in your region. So, it’s important to identify which species of birds have a very small wintering range, even among locally common species. We can use FeederWatch data to get an idea of what regions might hold special interest because they harbor unique species. So we listed the 10-most-widespread species for every FeederWatch region (see Figure 5 ) during each of the past 11 years. And when these lists were combined, 45 different species appeared on at least one top-10 list. Twelve of the 45 species (27 percent) were common in only one region. Ten of these 12 unique species were found in the West, which in some ways is not a fair comparison because FeederWatch regions are smaller in the East, and species are more likely to be found in more than one region. Also, some of the 12 species are more common than our list suggests; they just inhabit areas where few FeederWatchers live. (After all, how many of you would trade the possibility of negative-40-degree temperatures for the chance to have Boreal Chickadees come to your feeder?) In any case, our list of 12 species also shows that Anna’s Hummingbirds, California Towhees, and Golden-crowned Sparrows could face dire consequences if just one region, California, were to become a poor place to spend the winter. Top-10 lists also indicate interesting facts about the range of habitats within our FeederWatch regions. For example, the top-10 species were the same in the New England FeederWatch region every single year (see Figure 5), but in the Southwest, 17 different species appeared on at least one top-10 list. Does that mean New England is a boring place to be a FeederWatcher? No. This result indicates that even the common species in the Southwest are not as widely distributed as the common species in the Northeast. In New England, even the 10th-most-common species was found at 76 percent of all feeders on average, whereas the 10th-most-common species in the Southwest was seen only at 44 percent of all feeders. A quick look at an atlas will show how that can be: in the Southwest, FeederWatchers can live in low-elevation desert, higher-elevation grassland, still-higher sagebrush desert, or coniferous forest on mountains above the desert. Because of this wide range of bird habitats, it is less likely that all FeederWatchers in the Southwest will see the same species every year. Rare Birds As important as FeederWatch is for collecting data on common species, nothing is as exciting as finding a rare or unusual bird at your feeder. Comments such as, "I’ve never seen one before in more than 20 years of birding," from Dewey Boyer about seeing his first White-winged Crossbill are exciting to read. Even birds that are common to some FeederWatchers can be exciting finds elsewhere--take, for example, the Blue Jay that appeared in Pleasant View, Utah, or the Oregon Junco (the western form of the Dark-eyed Junco) that appeared in Bradley, Arkansas. But the Lewis’s Woodpecker that showed up at Brant Lake, New York (only the third record of this western species for the state), drew the most extensive media coverage, with photographs appearing in the Chestertown Chronicle and Field Notes, a joint publication of the American Birding Association and the National Audubon Society. (See "Woodpecker Central") "Common rarities" may seem like a contradiction in terms, but many FeederWatchers saw the same group of rarities last winter, because of the invasion of northern birds (see above). Many feeders in eastern Canada and the northeastern United States hosted White-winged Crossbills, while farther south, Red-breasted Nuthatches appeared in places where they are not the norm. "I have never seen this bird in this area before, and I have lived and birded here for 30 years," said Bess Mercer about the Red-breasted Nuthatch that appeared at her feeder in Kirksville, Missouri, last December. Yet another type of invading species was reported in 1997--98: the Eurasian Collared-Dove. This bird is not just moving into new wintering areas, it is also colonizing new breeding areas. Last winter, collared-doves were reported by FeederWatchers in Montgomery, Alabama; North Magnolia, Arkansas; and Shelton, Nebraska--the last of these being well away from the doves’ North American landing point in Florida. See "Anatomy of a Range Expansion" for more information about this fascinating species. It may only be a matter of time before these doves show up in your area. Other unusual species had solo sightings, or they were seen by very few people. Various warblers showed up far from their normal wintering grounds, including the following well-described or photographed birds: a Northern Parula in the Whitby’s yard in Ghent, New York; a Nashville Warbler at Paul Strickler’s feeder in Huntingdon Valley, Pennsylvania; a Black-throated Blue Warbler at Bonnie Finch’s feeder in Temple, Pennsylvania; and an Orange-crowned Warbler seen by Don MacNeill in Halifax, Nova Scotia. Roughly one quarter of our rare-bird reports this year were of birds visiting feeders, not to dine on the food provided by FeederWatchers, but to dine on the diners! FeederWatchers reported seeing Loggerhead Shrikes in Shipshaw and Lac-Megantic, Quebec; Gilsun, New Hampshire; and Louisville, Kentucky. More commonly reported, however, were hawks, with most of the descriptions suggesting that either Sharp-shinned or Cooper’s hawks were seen. Whereas these two hawks are not rare species, they are seen so seldom by most FeederWatchers that they received special mention. We had reports of these bird-eating hawks literally from coast (Seattle, Washington) to coast (Pawtucket, Rhode Island). Unfortunately, we received more reports of unusual and rare species than we have room to report. Thank you all for reporting your rarities, and a special thanks to those of you who photographed your interesting feeder visitors. This documentation is invaluable in confirming difficult-to-identify species and in ensuring that these important sightings become part of the ornithological record. We know the upcoming FeederWatch season will differ from the last--we won’t be expecting major finch invasions in the East, for instance--but we can’t wait to discover the unpredictable. Will last winter’s ice storm in the Northeast and last summer’s drought in the Southeast affect the birds we see at our feeders next season? As always, if you send the data, we’ll keep you posted. Project FeederWatch from an analyst's view "The data
collected by Project FeederWatch are extraordinary for scientific research," says Dr.
Hochaka. "The types of analyses we described in this year's annual report show what
can be done with a little curiosity and more than 10 years of data. |
