More info for the terms: altricial, cover, follicle, litter, population index, shrub, shrubs, tree
Migration: The arrival of Pacific band-tailed pigeons onto their breeding grounds occurs from March to June and peaks in April and June [11,26,84,85]. Fall migration into southern California and Mexico occurs from early August to mid-October and peaks in September [11,64,85], depending on weather conditions and food availability [11,64,85]. Migrating flocks of Pacific band-tailed pigeons in Arcata, California, were composed of 12 to 35 birds, and occasionally up to 200 birds [40].
Interior band-tailed pigeons arrive on their breeding grounds from late March to early May, peaking in late April. Fall migration to Mexico peaks in mid-September for populations in Colorado and Utah, and in mid-October for populations in Arizona and New Mexico [15].
Interior band-tailed pigeons display fidelity to the same general breeding areas each year. Of 2,314 interior band-tailed pigeons banded in central and western Colorado from 1969 to 1981, 92% returned to within 31 miles (50 km) of their previous breeding areas [77].
Mating: Band-tailed pigeons are monogamous [46] and pair bonds may last a lifetime [18]. Pacific and interior band-tailed pigeons breed from May to September [14,33,52], but because they are opportunistic [32], the breeding season may be extended or delayed, based on environmental conditions such as large masts of berries or other crops or favorable weather [32,43,54]. The breeding season of band-tailed pigeons is also dependent upon photoperiod length. The testes of captive Pacific band-tailed pigeons held in outdoor aviaries regressed with decreasing day length from September until December. After December, testes size began to increase again until March, when full breeding capability was reached. Female band-tailed pigeons kept in aviaries with males experienced no ovarian follicle growth until March [32,33].
Nesting: In California, nesting of Pacific band-tailed pigeons occurs from February until October [53,61], peaking from May to July [26,53,61]. Interior band-tailed pigeons nest from May to September [14].
Nests are composed of a loose platform of sticks [26,46,53,61,64] and forest litter [26] and are usually built on a strong horizontal branch of a tree or shrub [26,46,52,53]. Nest measurements for a Pacific band-tailed pigeon taken in Humboldt County, California, were: outside diameter, 7.8 inches (19.8 cm); inside diameter, 5.0 inches (12.7 cm); bowl depth, 1.3 inches (3.3 cm); and thickness under the bowl, 2.1 inches ( 5.3 cm) [26].
In the Oregon Coast Ranges, the mean height from the ground of 138 nests was 33.8 feet (10.3 m) in conifers, 33.5 feet (10.2 m) in deciduous trees and 14.4 feet (4.4 m) in shrubs [52]. Of 26 nests observed in shrubs and trees in Monterey County, California, nest height from the ground ranged from 12 to 95 feet (4-29 m), with an average height of 36 feet (11 m) [53]. Nesting may be semicolonial [64,83], with up to 17 nests in a single tree [64].
The band-tailed pigeon has the lowest breeding potential of any game bird in the United States [40,52,53]. Clutch size is typically 1 egg [32,33,40,46,52,53,64], but 2-egg [32,33,53,64] and 3-egg clutches have been reported. Of 219 interior and Pacific band-tailed pigeon clutches examined, 85% to 95% contained 1 egg [32,33,40,46,52,53,64]. Band-tailed pigeons typically nest once a year [40], but may complete up to 3 nest cycles per year during favorable weather conditions [32,33,46]. Of 134 radio-marked adult Pacific band-tailed pigeons, 60% initiated 2 to 3 nests during 1 breeding season, and 15% of all nesting birds produced 3 fledglings. Pacific band-tailed pigeons eliminated nesting intervals by overlapping nesting cycles (caring for 2 sets of offspring at different developmental stages) 78% of the time. This allowed for raising 3 broods in a 150-day nesting season. In western Oregon, the mean number of Pacific band-tailed pigeon nests initiated per year was 1.69/adult (n=137). Fifty-four percent initiated >2 nests/year and 10% produced 3 successful nests/year [52].
Incubation lasts 18 to 21 days [46,53,61,64]. Adult male and female band-tailed pigeons share brooding responsibilities of incubation and feeding [53,64,65]. Both parents incubate continuously, with males attending nests from mid-morning until mid-afternoon and females taking over from late afternoon to the following morning [53,61,64]. Young are altricial [64] and are fed "crop milk" produced in the crop of both parents [43,46,53,61] for the first few days after hatching, followed by a mixture of crop milk and regurgitated food [46].
Fledging: Juvenile band-tailed pigeons fledge between 20 and 28 days after hatching [53,61,64,65]. Fledging of Pacific band-tailed pigeons in western Oregon peaks in late August and early September [43].
Of 299 banded immature female interior band-tailed pigeons in Colorado, the mean dispersal distance from the nest to the recapture site the following year was 22.8 miles (36.7 km) (range 19.1 to 26.5 miles (30.7-42.7 km)). Of 298 males, dispersal distance from the nest was 16.2 miles (26.0 km) (range 13.1 to 19.2 miles (21.1-30.9 km)) [77].
Survival: Of 1,008 banded adult Pacific band-tailed pigeons recovered between 1965 and 1972, mean annual survival ranged from 44.5% to 85.3% and averaged 63.7% (95% confidence interval=7.6%) [43]. Mean annual survival rates for adult Pacific band-tailed pigeons were as follows:
State Years Mean annual survival rate (%) n California [84] 1952 to 1965 61.1 126 Oregon [94] 1952 to 1965 70.9 262 Washington [84] 1950 to 1965 62.2 128
Home range: The breeding home range of 70 radio-marked adult Pacific band-tailed pigeons on the Oregon Coast Ranges was 27,480 acres (11,121 ha ±60,040 acres (24,298 ha) (range 776-446,800 acres (314-180,800 ha)) [52]; however, the breeding home range in this geographic location may be less than 27,180 acres (11,000 ha) due to high mobility of band-tailed pigeons, as well as the limited range of variability in the distribution of habitats needed, and the high quality of habitat [74].
Pacific band-tailed pigeons are highly mobile during the breeding season, traveling an average of 3.1 miles (5.0 km) (s=4.6 miles (7.4 km)) to feeding areas [52]. Nesting territories of interior band-tailed pigeons in Humboldt County, California, ranged from a 0.10 mile (0.16 km) radius to a 0.50 mile (0.80 km) radius from the nest with a mean territorial radius of approximately 0.25 mile (0.40 km). Variability of territory size was attributable to irregularity of the terrain, proximity to a water source, and the abundance of forest cover [26].
Population trends: As of 2006, population monitoring techniques for the band-tailed pigeon needed further development for better accuracy [46,52,84,85]. In the western United States and Canada, band-tailed pigeon populations have experienced a significant (P<0.10) negative trend of -3.5% total, according to Breeding Bird Surveys conducted from 1968 to 1991 [39]. The population index of band-tailed pigeons in the late 1980's was only 30% to 50% of that in the 1960s [43].
The population index of Pacific band-tailed pigeons indicated an average rate of increase of +2.4% per year from 1950 to the early 1960s, a downward trend of -10.4% per year from the mid-1960s to the mid-1970s, an increase of +7.1% per year from the mid-1970s to the early 1980s, and another decrease of -11.1% per year from the mid- to late 1980s [43].