Degree of Threat: AB
Comments: The primary threats are habitat loss (both nesting and feeding) and hunting (Bancroft and Bowman 2001).
HABITAT LOSS: A pervasive threat is loss and fragmentation of hardwood forest feeding habitat and mangrove-island nesting habitat (Strong and Bancroft 1994a, Bancroft et al. 2000, Bancroft and Bowman 2001). Clearing of land for agriculture, urban areas, resorts, and other commercial activities has degraded and reduced available habitat throughout the range. Accelerated drilling and filling of mangroves and clearing of upland feeding areas continues.
Continued destruction of hardwood forest throughout the Florida Keys is likely the most serious and increasing threat to the U.S. population. Because young birds require larger patches of forest, continued fragmentation of the remaining hammocks will likely reduce successful recruitment of young birds into the population and increase the vulnerability of young and mature pigeons to predation (Strong and Bancroft 1994). Destruction and fragmentation of forest decreases fruit supplies and increases the disturbance of birds feeding in remaining trees (Bancroft 1992). Strong and Bancroft (1994b) estimated from Long Key north to the Ragged Keys over 40% of the seasonal deciduous forests and 15% of the mangrove forests have been cleared for development. Further loss of habitat will continue to threaten the south Florida population (Strong et al. 1994). Degradation of foraging habitat may already be affecting the behavior of the Florida population. The increasing numbers of birds feeding in pinelands north of Florida Bay (Ogden 1973) suggest that some birds may already be resorting to atypical habitats.
In Puerto Rico, Wiley (1985) estimated that less than 0.2% of the original forests remained. The factors that have contributed to declining populations in Puerto Rico have also affected many other species. Raffaele (1983) cited 49 of 51 avian endangerments on Puerto Rico as being precipitated by habitat destruction and disturbance.
HUNTING: Illegal harvesting of squabs and shooting of nesting adults may limit reproductive success throughout much of the range (Strong and Bancroft 1994a, Bancroft and Bowman 2001). Severe hunting pressure and collecting of squabs in the Bahamas and other Caribbean nesting grounds has reduced numbers and has been a major reason for this species' demise (Raffaele 1985). Biaggi (1970) described the species as diminishing alarmingly in Puerto Rico, presumably from pressures related to hunting (Owre 1978). Pigeons are especially vulnerable early in the nesting season because their populations are highly localized at nesting colonies and make regular flights between these sites and feeding/watering sites. In addition, recently fledged young are less wary (Wiley 1979).
HUMAN DISTURBANCE: White-crowned pigeons are very wary of human activity and are sensitive to human activity, which may deter them from potential foraging areas and may render potential nesting areas unsuitable.
PREDATION: Colonization of nesting islands by raccoons may represent a serious threat to breeding populations. Currently, the distribution of raccoons on mangrove keys is limited by the distance from the mainland or mainline keys and by the frequency of major hurricanes (Bancroft 1992). Locally, human habitation has also facilitated local increases in populations (Strong et al. 1991). It appears that, with few exceptions, white-crowned pigeons will not nest on islands that have been occupied by raccoons (Strong et al. 1991). Expansion of raccoons into more keys in Florida Bay is likely to make more islands unsuitable for nesting.
NATURAL DISTURBANCES: Because over 75% of the nesting population in the Upper Florida Keys have been estimated to breed on 16 keys, this population may be especially vulnerable to hurricanes (Strong et al. 1995).