Demography and Populations

Age At First Breeding; Intervals Between Breeding

Not known.

Clutch

See Breeding: eggs, above.

Annual And Lifetime Reproductive Success

Three of 6 nests Tanner (1941) found in the Singer Tract were successful in producing 1 young each. Chicks in the other nests were lost soon after hatching. Between 1931 and 1939, at least 19 young in 9 broods were observed out of the nest, averaging 2.11 young/brood (Tanner 1941, 1942a).

Number Of Broods Normally Reared Per Season

One (Tanner 1942a).

Proportion Of Total Females That Rear At Least One Brood To Independence

No estimates available. Of 6 nests observed in the Singer Tract, only 3 fledged young (Tanner 1941, 1942a).

No data.

Diseases

No information.

Body Parasites

One nest from which chicks disappeared shortly after hatching was alive with mites (Tanner 1941).

Natural Mortality

No natural mortality documented. See Behavior: predation, above. By virtue of its status as a resident living in Cuba and in coastal plain ecosystems of the se. U.S., Ivory-billed Woodpecker was influenced by catastrophic weather events somewhat unique to the region: hurricanes, lightning, and lightning-caused fires can be important in providing a continuous adequate supply of dead trees for nesting and roosting and as habitat for the beetle larvae the woodpeckers fed on. However, these events can also kill birds. The larger (hence often taller) trees needed for cavity excavation would be especially vulnerable to lightning strike, and Ivory-billeds were probably occasionally killed when roost or nest trees were struck.

A female specimen (Univ. of Iowa #28792) is missing about half of digits 1 and 4 on left foot, but toes are healed, an injury with an unknown cause, but one that the bird survived.

Killing By Humans

For many reasons: curiosity; food; symbols of war worn and used in medicine bundles by Native Americans; as items to be collected, traded, and sold; and as scientific specimens. Ivory-billeds had market value among Native Americans who seemed to view the bill as a totem of successful warfare (Jackson in press), and mortality caused by Native Americans likely increased dramatically following the introduction of firearms to their culture.

Market value among colonial Americans was because of the size and color of the bill. Audubon (1842: 216) noted that at refueling stops, travelers on steamboats often paid “a quarter of a dollar for two or three heads of this woodpecker” as souvenirs. A century later, residents of the Gulf Hammock and lower Suwannee River region of the upper Florida Peninsula considered the bill of Ivory-billeds to be “real” ivory and sold the bills for as much as $5 apiece (Tanner 1942a).

The era of Victorian natural-history collections and the growth of scientific ornithology that blos-somed in the second half of the nineteenth century led to further killing and inflation of the species’ economic value. Chapman (1930) suggested the number of specimens collected probably did not exceed 250, but the number killed for or by collectors likely exceeded 500. Hahn (1963) and Jackson (in press) demonstrate that >400 specimens were taken, most between 1880 and 1910 (Fig. 5). In 1884, the asking price for a pair of Ivory-billeds was $20 (Ellis and Webster 1884); by 1905, they brought $40–50 each (Phillips 1926). Arthur T. Wayne, of Charleston, SC, a major trader in Ivory-billed specimens, advertised them in the Auk (Wayne 1894); he “encountered” >200 Ivory-billeds in Florida between 1892 and 1894 (Wayne 1910), and certainly collected many of them.

Remains of many Ivory-billeds have been found in archaeological excavations, some that include skeletal elements other than the skull and bill, perhaps providing evidence of the northern limits of the species (e.g., Illinois [Parmalee 1958], Ohio [Wetmore 1943, Murphy and Farrand 1979], n. Georgia [Van der Schalie and Parmalee 1960]); others clearly extralimital or only including the bill are likely indicative of the trade in bills of the species. Jackson (in press) discusses human uses of Ivory-billeds.

In Cuba, Lamb (1957) collected information on Ivory-billed mortality and learned of 3 killed for sport, 8 killed for food, 3 killed to satisfy curiosity, one nestling that died after it was removed from its nest, and 2 additional kills for which no motive was given. Methods used to kill birds in Cuba varied from using stones to guns to plugging cavity entrances and cutting the cavity tree down. A female kept in captivity eventually escaped.

Generally sedentary (Allen and Kellogg 1937); but likely nomadic as habitats were altered or destroyed (Tanner 1942a) or if local populations increased beyond carrying capacity of local environment.

Initial Dispersal From Natal Site

No dispersal distances known. Dispersal occurred at least 3 mo and perhaps up to 1 yr following fledging (Tanner 1942a).

Fidelity To Breeding Site And Winter Home Range

So long as habitat remained, birds seemed to be sedentary, sometimes using same nest tree in >1 yr (Tanner 1942a).

Dispersal From Breeding Site

No data.

Home Range

The concepts of home range and territory are often confused, even among biologists: Home range refers to the area used by an animal in the course of its daily activities; a territory is any defended area. We have no descriptions of territorial defense by Ivory-billed Woodpeckers.

Home ranges of birds typically determined by following or otherwise monitoring movements of marked individuals, plotting their locations at in-tervals, and connecting locations to define a home range. Only 1 Ivory-billed Woodpecker was ever marked (a nestling banded by Tanner on 6 Mar 1938, band 365-27264; fide M. Gustafson, Bird Banding Laboratory), and Tanner only occasionally noted having observed it over its first year. However, Tanner (1942a) followed unmarked individuals from their roosts and noted that, during the nesting season, they often traveled 1.2–2.4 km from the nest. A lone male with a recognizable plumage pattern traveled as far as 4.0 km its nest in the course of his daily activities. As a result of anecdotal information, Tanner believed that winter ranges were much larger than nesting-season ranges.

Species likely extinct in both the U.S. and Cuba. If not, it is hanging on by the slimmest of threads as a result of its probable longevity, wariness, and the inhospitable nature of its habitat.

Numbers

As a function of its large size, need for large trees in which to excavate nest and roost cavities, and dependence on concentrations of large wood-boring beetle larvae that are associated with recently dead trees, the Ivory-billed Woodpecker needed large home ranges and thus vast forested areas. Its populations were probably never large and were limited to habitats that sustained high tree mortality—areas that flooded or burned regularly or were subject to the devastating impacts of hurricanes. Allen and Kellogg (1937) suggested that the Ivory-billed was characteristically sedentary and might live its entire life in one area, establishing small, local populations isolated from other such populations. Evidence sup-porting this suggestion includes observations in the Singer Tract of Louisiana (e.g., Allen and Kellogg 1937, Allen 1939, Tanner 1942a) and records of large numbers of specimens collected from various discrete, isolated areas (Jackson in press).

Trends

Throughout recorded history, a downward trend, linked to fragmentation and destruction of habitat and killing of the birds for various reasons. As numbers declined and populations became more isolated from one another, remaining populations also became more accessible and vulnerable. Accompanying these biogeographic changes were human social changes (e.g., values placed on the birds leading to increased killing) and technological changes (e.g., better transportation, better firearms) that increased the downward spiral. Using Ivory-billed specimen collection data from Hahn 1963 (see also Fig. 5), Tanner (pers. comm., annotations of Tanner 1942a) noted that the last date of collection of an Ivory-billed in an area is correlated with the total number collected in the region. In general, birds survived the longest where their populations were the highest, with n. and s. Florida populations the last to go. The most recently documented population in the U.S., however, the Singer Tract (Louisiana) population, does not fit this model, perhaps because it was not known outside of the local area.

Not studied; no data. Populations probably always limited by availability of habitat, including adequately large trees for roosts and a reliable supply of food within flight distance from nests. Nothing known of intraspecific territoriality, but the Ivory-billed was social in that members of a pair nearly always traveled together, thus perhaps facilitating establishment of new populations as habitat was lost or new habitat became available.