The beautiful Eurasian collared-dove is adorned in muted grays, browns, and whites, and has a distinct dark crescent on its neck. Its incessant cooing is gentle and familiar to city and farm dwellers throughout Europe and North America.
Before its unprecedented expansion across Eurasia and later North America, it resided in southern Asia from Turkey to southern China and from India south to Sri Lanka. At the beginning of the 20th century, collared-doves began dispersing westward and then northward, reaching Britain in 1953 and breeding by 1955, arriving in Ireland in 1959, and Iceland by 1964 (although it has never become established there). Collared-doves also expanded eastward to southern Russia, most of China, and even Japan (where they may have been introduced), and southward to Egypt, Morocco and the Canary Islands. This rapid rate of expansion has been estimated at 27 miles/year; not bad for a non-migratory, but obviously highly dispersive, species. Today collared-doves are ubiquitous in towns and countryside throughout Europe and Asia, where they seems to be comfortably coexisting with their avian neighbours.
But that’s not quite the end of the story.
The invasion of collared-doves in North America began when a small flock escaped captivity in Nassau, Bahamas in 1974. By 1982, collared-doves had arrived in in Florida, where they rapidly began expanding, and then very quickly moved to nearby states (see Figure 1 below). By 2005, collared-doves had arrived in Vancouver, British Columbia (BC) in Canada, greatly surpassing expansion estimates (see Figure 2 from BC Bird Atlas). Given their arrival in southern Florida in 1982, collared-doves have dispersed across the approximate 2,800 mile distance between Miami and Vancouver at a phenomenal rate of ~128 miles/year, much faster than estimated dispersal rates in Europe (i.e., 27 miles/year) and for other introduced species such as starlings and House Sparrows in North America (see estimates below).
Figure 1. BBS route results for 2007 survey. Dark circles indicate collared-dove presence and abundance.
Figure 2: Eurasian collared-dove distribution in British Columbia, Canada between 2008 and 2012.
Expansions of other introduced species in North America are also well documented. European starlings were first introduced in Central Park, New York in 1890 and 1891, and by 1959 had reached Vancouver, BC on the west coast. Starlings had made the approximate 2,400 mile journey at a dispersal rate of about 42 miles/year. House Sparrows have a similar history of dispersal. First released and established in New York between 1851 and 1855, they were first reported in the Vancouver area around 1900. House Sparrows made the 2,400 mile journey to Vancouver at a dispersal rate of about 49 miles/year, very similar to starlings. In contrast, collared-doves have dispersed at a much more rapid rate (128 miles/year).
So, how concerned should we be for our native fauna, particularly other dove species such as Mourning Dove and Common Ground-dove? Recent research suggests that inter-species competition may not be a significant issue. For example, the size of seeds selected by mourning doves and collared-doves is quite different, “which may limit foraging competition between these species” and collared doves are not overly aggressive. Collared-doves may take over other nests (e.g., American Robin), but this affect has not been widely documented and is likely not a major issue. As well, there has been some concern that collared-doves could transmit new pathogens or infectious diseases to native bird species, but evidence of inter-species transmission in collared-doves has not been well documented.
So should we be concerned or impressed? Is this a good news story when accounts of bird extirpation and range retractions are almost a daily event? Should we embrace the increased species richness or alpha diversity in our local towns and gardens? Do collared-doves bring satisfaction and joy to urban dwellers who rarely move beyond their city gates? One thing is for certain, Eurasian collared-doves are here to stay. I can only be impressed by their versatility, adaptability, and tenacity as they have settled into their new homes.