Alan D. Wilson
North America is going to the doves! Many pigeons and doves in the family Columbidae are undergoing a rapid range expansion across North America. If you live anywhere south of an imaginary line extending from southern Alaska to Newfoundland, you have certainly come in contact with a dove of one type or another. But it has not always been that way. The dynamic range expansions that many doves have undergone, and are undergoing, are spectacular, and the stories are captivating. Using information from eBird
and the Christmas Bird Count,
we can read some of these dove "stories," and you will see that from a birder's point of
Alan D Wilson
view, North America certainly seems to be going to the doves!
Where are the doves coming from? Some dove species found across North America have been introduced. The Rock Pigeon (Columba livia), the common city pigeon, was introduced from Europe more than 200 years ago. More recently, the Eurasian Collared-Dove (Streptopelia decaocto), introduced initially in the Bahamas in the early 1970s, is expanding its range across North America through great leaps and bounds--first reported in South Florida in the late 1980s, this dove is now being reported
Alan D. Wilson
in Minnesota. Some dove species native to North America are also colonizing new regions. At the turn of the century, the Mourning Dove (Zenaida macroura
), for example, either did not occur or was very uncommon across all of Canada and the northern part of the United States. Now it is one of the most common birds in these areas. The White-winged Dove (Zenaida asiatica
), a common nesting bird in South Texas, is expanding its range throughout that state and into Louisiana. The introduced populations of this species in Florida are exploding. Initially released from a private aviary in South Florida and then introduced in central Florida, the dove is rapidly expanding throughout the entire state. Other dove species are also increasing: Inca Dove (Columbina inca
) numbers are slowly increasing and expanding through parts of Texas, Louisiana, and Arkansas, and wintering Ruddy Ground-Doves (Columbina talpacoti
) have become so regular in Arizona that the state's Rare Bird Committee removed it from its review list.
Mapping dove populations over time is an excellent way to demonstrate the population dynamics of wild bird species. The National Audubon Society's Christmas Bird Count, an early-winter survey of North American Bird Populations that has been taking place for over 100 years, is an excellent source of information about bird population trends. Results from the past 50 Christmas Bird Counts (CBCs) clearly show the range expansion of Mourning Doves, (see map 1), which have become one of the most common birds in North America.
Map 1: Mourning Dove. This animated map shows the change in Mourning Dove abundance in ten-year increments between 1950 and 1998 based on Christmas Bird Count (CBC) results. Each dot represents the highest reported number of birds per party hour for each 10-year interval. Circles represent CBCs that reported Mourning Doves. Both circle size and color indicate the number of birds per party hour. Small squares represent CBCs that did not report Mourning Doves. To view animation, click on map.
Since 1950, the total number of counts reporting Mourning Dove has increased by 20 percent; this means that more than 80 percent of all North American CBCs are finding this species. White-winged Doves are being counted during CBCs from Texas through Florida in higher and higher numbers (see map 2). They have occurred regularly in extreme South Texas, but beginning in the late 1970s they began colonizing areas in other regions, and their numbers have increased dramatically. In Florida, White-winged Doves have been irregularly reported in the panhandle. But released birds in South and central Florida are undergoing an explosive expansion. Since the late 1970s, the Eurasian Collared-Dove has been expanding rapidly throughout Florida and neighboring states (see map 3). The CBC database shows us just how rapid this expansion is. In coming years it will be exciting to watch the spread of this non-native species throughout all of North America.
Why are doves expanding their ranges? Several reasons exist. Many dove species prefer urban or suburban areas. The rapid increase in urban population centers has certainly influenced the expansion of the Rock Dove. White-winged Doves, Eurasian Collared-Doves, and Mourning Doves are benefiting from the increased urbanization of both Texas and Florida. The rapid expansion of agriculture practices and the increased popularity of backyard bird feeding during the 20th century has contributed to the expansion of many dove species. For example, the increased Mourning Dove numbers in southern Ontario are closely correlated to an increase in the amount of acreage planted in corn, on which they feed. Also, doves are opportunistic breeders; many species will nest almost anytime of year. Rock Doves and White-winged Doves brood young anytime, and Eurasian Collared-Doves have been observed nesting in every month except January. Finally, doves may have benefited by warmer winter temperatures across North America in recent years. The feet of many dove species, including Mourning and White-winged doves, are susceptible to frostbite during extremely cold winter conditions. Consequently, they must weigh the advantage of overwintering farther north and the stresses of a harsher climate, against the potential for early season nesting and producing multiple broods of young. Warmer winters decrease the possibility of frostbite, allowing susceptible species to winter farther north.
Monitoring the range expansions of North America's dove and pigeon species will allow us to observe the consequences of these expansions. We'll be able to ask-and hopefully answer-questions such as these: What effects does the expansion of one bird species have on other bird populations? Will the increase in Eurasian Collared-Doves have an adverse effect on the similar Mourning Dove? How fast and how far will these expansions take place?
Continent wide monitoring projects like the Christmas Bird Count, Project FeederWatch, Breeding Bird Survey, and the Great Backyard Bird Count enable us to keep track of changing bird populations. The success of these projects depends on the participation of interested citizens willing to contribute their observations. We encourage you to get involved and help scientists learn more about the changing bird landscape as you learn more about birds.
--Steve Kelling, Cornell Lab of Ornithology
Map 2: White-winged Dove. This animated map shows the change in White-winged Dove abundance in 10-year increments between 1950 and 1998 based on Christmas Bird Count (CBC) results. Each dot represents the highest reported number of birds per party hour for each ten-year interval. Circles represent CBCs that reported White-winged Doves. Both circle size and color indicate the number of birds per party hour. Small squares represent CBCs that did not report White-winged Doves. To view animation, click on map.
Map 3: Eurasian Collared Dove. This animated map shows the spread of Eurasian Collared-Doves from their first reports during Christmas Bird Counts (CBCs) (in 1988) through the 1998 CBC season. Each dot represents the number of birds per party hour. Both circle size and color indicate the number of birds per party hour. Small squares represent CBCs that did not report Eurasian Collared-Doves. To view animation, click on map.