{"id":14276,"date":"2011-04-15T09:38:59","date_gmt":"2011-04-15T13:38:59","guid":{"rendered":"https:\/\/www.allaboutbirds.org\/news\/?p=14276"},"modified":"2015-06-09T09:45:20","modified_gmt":"2015-06-09T13:45:20","slug":"vultures-riding-north","status":"publish","type":"post","link":"https:\/\/www.allaboutbirds.org\/news\/vultures-riding-north\/","title":{"rendered":"Vultures Riding North"},"content":{"rendered":"<div class=\"wp-block-group sidebar-alignright sidebar-space order-bottom\"><div class=\"article-list list-style alignright\"><h2 class=\"article-list-header\">More From Living Bird<\/h2><ul><li class=\"article-item\"><div class=\"article-item-container\"><div class=\"article-item-media  content-living-bird-toc\"><figure class=\"article-item-media-ratio\"><img decoding=\"async\" src=\"https:\/\/www.allaboutbirds.org\/news\/wp-content\/uploads\/2015\/05\/lb_toc_spread.jpg\" srcset=\"https:\/\/www.allaboutbirds.org\/news\/wp-content\/uploads\/2015\/05\/lb_toc_spread-720x329.jpg 720w, https:\/\/www.allaboutbirds.org\/news\/wp-content\/uploads\/2015\/05\/lb_toc_spread-768x351.jpg 768w, https:\/\/www.allaboutbirds.org\/news\/wp-content\/uploads\/2015\/05\/lb_toc_spread-480x219.jpg 480w, https:\/\/www.allaboutbirds.org\/news\/wp-content\/uploads\/2015\/05\/lb_toc_spread.jpg 918w\" sizes=\"\" alt=\"hummingbirds by Lois Manowitz\" loading=\"lazy\" \/><\/figure><\/div><div class=\"article-item-body\"><span class=\"article-item-header\">Living Bird Spring 2011\u2014Table of Contents<\/span><\/div><\/div><\/li><li class=\"article-item\"><div class=\"article-item-container\"><div class=\"article-item-media  content-living-bird-toc\"><figure class=\"article-item-media-ratio\"><img decoding=\"async\" src=\"https:\/\/www.allaboutbirds.org\/news\/wp-content\/uploads\/2023\/07\/living-bird-latest.png\" srcset=\"https:\/\/www.allaboutbirds.org\/news\/wp-content\/uploads\/2023\/07\/living-bird-latest.png 720w, https:\/\/www.allaboutbirds.org\/news\/wp-content\/uploads\/2023\/07\/living-bird-latest-240x180.png 240w, https:\/\/www.allaboutbirds.org\/news\/wp-content\/uploads\/2023\/07\/living-bird-latest-480x360.png 480w\" sizes=\"\" alt=\"Living Bird-latest issue\" loading=\"lazy\" \/><\/figure><\/div><div class=\"article-item-body\"><span class=\"article-item-header\">Living Bird Magazine\u2014Latest Issue<\/span><\/div><\/div><\/li><li class=\"article-item\"><div class=\"article-item-container\"><div class=\"article-item-media  content-article\"><figure class=\"article-item-media-ratio\"><img decoding=\"async\" src=\"https:\/\/www.allaboutbirds.org\/news\/wp-content\/uploads\/2023\/07\/living-bird-acrhive.png\" srcset=\"https:\/\/www.allaboutbirds.org\/news\/wp-content\/uploads\/2023\/07\/living-bird-acrhive.png 720w, https:\/\/www.allaboutbirds.org\/news\/wp-content\/uploads\/2023\/07\/living-bird-acrhive-240x180.png 240w, https:\/\/www.allaboutbirds.org\/news\/wp-content\/uploads\/2023\/07\/living-bird-acrhive-480x360.png 480w\" sizes=\"\" alt=\"Living Bird archives\" loading=\"lazy\" \/><\/figure><\/div><div class=\"article-item-body\"><span class=\"article-item-header\">Living Bird Magazine Archives<\/span><\/div><\/div><\/li><\/ul><\/div><\/div>\n<div class=\"wp-block-group sidebar-alignright sidebar-space order-bottom\"><!--HubSpot Call-to-Action Code -->\r\n<span class=\"hs-cta-wrapper\" id=\"hs-cta-wrapper-096b8ce3-0e2d-46c5-bbf7-12de3323c8da\">\r\n    <span class=\"hs-cta-node hs-cta-096b8ce3-0e2d-46c5-bbf7-12de3323c8da\" id=\"hs-cta-096b8ce3-0e2d-46c5-bbf7-12de3323c8da\">\r\n        <!--[if lte IE 8]><div id=\"hs-cta-ie-element\"><\/div><![endif]-->\r\n        <a href=\"http:\/\/cta-redirect.hubspot.com\/cta\/redirect\/95627\/096b8ce3-0e2d-46c5-bbf7-12de3323c8da\" ><img decoding=\"async\" class=\"hs-cta-img\" id=\"hs-cta-img-096b8ce3-0e2d-46c5-bbf7-12de3323c8da\" style=\"border-width:0px;\" src=\"https:\/\/no-cache.hubspot.com\/cta\/default\/95627\/096b8ce3-0e2d-46c5-bbf7-12de3323c8da.png\"  alt=\"subscribe to Living Bird magazine\" loading=\"lazy\" \/><\/a>\r\n    <\/span>\r\n    <script charset=\"utf-8\" src=\"https:\/\/js.hscta.net\/cta\/current.js\"><\/script>\r\n    <script type=\"text\/javascript\">\r\n        hbspt.cta.load(95627, '096b8ce3-0e2d-46c5-bbf7-12de3323c8da', {});\r\n    <\/script>\r\n<\/span>\r\n<!-- end HubSpot Call-to-Action Code -->\r\n\r\n<\/div>\n\n<p>Not so long ago\u2014a blink of an eye on the geological time scale\u2014Turkey Vultures soared only over southern landscapes. Today, you can spot them from Maine and Ontario to Montana, Saskatchewan, Manitoba, and even north and west to Vancouver Island, British Columbia.<\/p>\n<p>They are part of a cluster of \u201csouthern species\u201d\u2014Red-bellied Woodpecker, Tufted Titmouse, Northern Cardinal, Northern Mockingbird, and Carolina Wren\u2014that have pushed their ranges hundreds of miles north in recent decades. A century ago, all were far more numerous south of the Mason-Dixon Line than north of it. Today, all are common throughout most of New England and other northern states west to the Great Lakes, and three of them\u2014Turkey Vulture, cardinal, and mockingbird\u2014now nest regularly in Canada.<\/p>\n<p>The idea that a warming continent might cause such a movement dates back at least to 1909, when Philadelphia ornithologist Spencer Trotter published \u201cThe Geological and Geographical Relations of the Land-Bird Fauna of Northeastern America\u201d in <em>The Auk<\/em>. Trotter had a much different understanding of climate change than we have today. In his view, the three recognized avian faunas of the day\u2014the \u201cCanadian,\u201d the \u201cAlleghanian,\u201d and the \u201cCarolinian\u201d\u2014had followed one another to the northeastern corner of the continent in a slow and stately pageant. They had moved, he believed, in response to \u201ca general tendency of various species of birds to spread gradually northward into a region of new environing conditions which has been opened to them since the Glacial Period.\u201d After the ice receded and conifers took hold, Golden-crowned Kinglets, Pine Grosbeaks, redpolls, juncos, and other Canadian species had pushed in first. Much later, as the habitat changed still more, bluebirds, goldfinches, Chipping Sparrows, Rose-breasted Grosbeaks, Red-winged Blackbirds, and other Alleghanians moved in. Finally, in the first decade of the 20th century, the Carolinian species, the \u201claggards,\u201d seemed poised to colonize the Northeast. Trotter listed the Tufted Titmouse, Northern Cardinal, Carolina Wren, and Turkey \u201cBuzzard\u201d as species on their way\u2014and he has been proven correct in each case.<\/p>\n<p>Twenty years later, George Miksch Sutton observed in \u201cExtension of the Breeding Range of the Turkey Vulture in Pennsylvania\u201d (<em>The Auk<\/em>, 1928) that Pennsylvania observers had seen vultures and nests \u201cwhere natives had never seen a vulture before.\u201d He dismissed rising temperatures as the reason, however. \u201cChange of climate has probably had nothing to do with the extension of the range of this species; the immediate cause is not difficult to trace. Deer have become so abundant in some sections of the [state] that they have exhausted their food supply, and are dying by the score as the result of undernourishment.\u201d<\/p>\n<p>Sutton\u2019s explanation may still be the majority view. I\u2019ve often said it myself: \u201cToo many deer, too many roads, too many cars. Vultures are feasting on all those road-kills. It\u2019s obvious.\u201d<\/p>\n<p>Maybe it\u2019s a little too obvious. It is true that white-tailed deer populations have exploded over the same decades that vultures have moved northward. From a population of about half a million in 1900, white-tailed deer now number at least 15 million and, according to some estimates, well over 20 million. They have become a scourge for gardeners, farmers, foresters, park rangers, and drivers. The National Highway Traffic Safety Administration recently concluded that the 1.5 million accidents involving vehicles and deer, 150 human fatalities, 10,000 injuries, and one billion dollars in damages recorded each year represent only a fraction of the damages because countless accidents go unreported.<\/p>\n<p>Despite these statistics, however, I have begun to wonder whether our birders\u2019 sense that vultures depend on deer carcasses might be based on a kind of optical illusion. Yes, we all see lots of road-killed deer and, yes, sometimes we see vultures standing alongside the carcasses and occasionally even feeding on them. But, how often do we identify the smaller, squishier road-kills vultures also feast on? And how much do we know about the carrion that vultures find away from roadsides?<\/p>\n<p>In their 1998 <em>Birds of North America<\/em> monograph on the species, David Kirk and Michael Mossman note that Turkey Vultures feed \u201copportunistically on [a] wide range of wild and domestic carrion,\u201d including mice, shrews, deer, pigs, sheep, chickens, blackbirds, snakes, turtles, shrimp, snails, grasshoppers, mayflies, coyotes, sea lions, and more. They also eat cow manure and rotten pumpkins.<\/p>\n<p>The feeding habits of vultures are commonly studied by collecting and analyzing the birds\u2019 regurgitated pellets. A browse through the literature suggests that deer kills are not as crucial a component in vultures\u2019 diets as birders might expect. A 1984 study of vultures in Virginia published in <em>The Wilson Bulletin<\/em> found that the remains of sheep (in 55 percent of all pellets) and opossum (in 51 percent) outnumbered deer remains (32 percent). A 1989 study, \u201cFood Habits of Turkey Vultures in West Texas,\u201d published in <em>The Journal of Raptor Research<\/em>, found deer remains in fewer than 8 percent of the pellets collected. By contrast, skunk remains were found in 37 percent and rabbit remains in 89 percent.<\/p>\n<p>Another study published in <em>The Wilson Bulletin<\/em> (1990) found that in Maryland and Pennsylvania, where white-tailed deer are especially abundant, vultures fed on both domestic poultry (64 percent of all pellets) and domestic animals (50 percent) more often than on deer (40 percent). Another 1990 article in <em>The Wilson Bulletin<\/em>, \u201cTurkey Vulture Food Habits in Southern Ontario,\u201d reported that vultures at the roosts studied had fed on a wide mix of 19 mammals, both domestic and wild, as well as on beetles and chickens. Woodchuck was the most widely taken food, present in 53 percent of the pellets. White-tailed deer did not even make the menu.<\/p>\n<p>Could such an adaptable bird have been waiting for a white-tailed deer explosion to fuel a northward expansion?<\/p>\n<p>Kirk and Mossman note the deer increase as one factor among several that have led to the continentwide increase of Turkey Vultures. Declines in both persecution and pesticides have also contributed, they report. Vultures are trapped and shot less often than they were decades ago, and, like hawks and other flesh-eating birds, vultures are healthier now because organochlorines are less prominent in the food chain. The authors also observe that farming practices have changed in the southern states, in a general trend away from family animal-based operations toward larger cash-crop farms with better disposal of dead livestock. Different forestry practices have led to the loss of nesting habitat in the south as well. Both of these developments may have helped push the vultures northward to new feeding and nesting areas.<\/p>\n<p>Although Kirk and Mossman do not mention it, I can\u2019t help wondering whether climate change has also contributed. The near-century-long pattern of their invasion suggests it. Vultures have followed the same sequence in each step northward as they pushed through Pennsylvania and into New Jersey in the 1930s, into southern New York and southern New England in the 1940s, and, after a delay of a quarter-century (possibly caused by pesticides), north into Upstate New York, northern New England, and southern Canada in recent decades. At each step the first vagrant birds were seen in spring and summer over a period of a year or two, a handful of nests were found a few years later, and soon, only 20 or 30 years after the first rarities appeared, the species had taken up permanent residency in an area where once it could not be found.<\/p>\n<p>I haven\u2019t been able to find a study making a direct link between the vulture increase and climate change, but a recent report by British ornithologist Christopher J. Butler, published in <em>The Ibis<\/em> in 2003, comes close. Butler compiled a century\u2019s worth of records from two bird clubs\u2014the Cayuga Bird Club for the Cayuga Lake Basin (Ithaca, New York) and the Worcester County Bird Club (Worcester, Massachusetts)\u2014to investigate first arrival dates for short-term migrants in those areas. Just as similar studies of European migrants found, Butler discovered that virtually all short-distance migrants had shifted their migration ahead, apparently in response to climate change. The Worcester data indicated that 49 of the 52 species, including the Turkey Vulture, had moved toward significantly earlier arrival dates. The Cayuga Bird Club data showed this trend even more clearly. Here Butler was able to compare the first-arrival dates club members reported from 1903 to 1950 with the club\u2019s reports from 1951 to 1993. All but two of the 47 short-distance migrants had shifted their arrival dates ahead in the year. The shift in Turkey Vulture migration has been particularly obvious. For the first half of the 20th century their average arrival date was April 20; for the second half it was nearly a month earlier, March 22.<\/p>\n<p>The threats of climate change frighten us\u2014as they should. But I will give the last words to Spencer Trotter, whose rosier perspective can only be shared if we can imagine far beyond human history and experience, both backward and forward in time: \u201cFrom our limited point of view the array of species and varieties which we see today seem peculiarly stable in their features and their adaptations. But the dynamic influences of environment are ceaseless if inconspicuous. Species and faunas alike are but passing phases in the vast cosmic processes of a continent\u2019s history.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Not so long ago\u2014a blink of an eye on the geological time scale\u2014Turkey Vultures soared only over southern landscapes. Today, you can spot them from Maine and Ontario to Montana,<a class=\"excerpt-read-more\" href=\"https:\/\/www.allaboutbirds.org\/news\/vultures-riding-north\/\" title=\"ReadVultures Riding North\">&#8230; Read more 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