In
the United States the Roseate Spoonbill breeds in only three states: Florida, Louisiana,
and Texas. Although Roseate Spoonbills
probably never were extremely abundant in Texas, they were virtually extirpated there
between 1850 and 1919 because of encroaching civilization and exploitation by the
millinery trade (Allen 1942). However, with
the advent of laws to protect colonial nesting birds, Roseate Spoonbill numbers have
gradually increased; yearly estimates of the number of breeding pairs in coastal Texas
during the last two decades vary from about 1,400 to 2,500 (Texas Colonial Waterbird
Society 1982, Texas Parks and Wildlife Dept. 1992). Spoonbills
also winter in Texas, but usually in fewer numbers, and they may wander irregularly along
water courses to more northerly counties after the breeding season (Texas Ornithological
Society 1995); some birds have been sighted as far north as Amarillo in autumn (Oberholser
1974). DISTRIBUTION:
The breeding range of the Roseate Spoonbill extends for over 800 km (500 mi) along the
Texas coast, from the vicinity of Port Arthur in the north to that of Port Isabel in the
south. The TBBAP findings confirmed breeding
(76% of total nest records) in all of Texas's coastal counties and several inland
counties. The most inland confirmed TBBAP
nest locations were at Addicks Reservoir, quads H-7 and H-8 in latilong 29095, and at Lake
Texana, quad F-3 in latilong 29096. The most
inland probable nest locale was Somerville Lake, quad C6 in latilong 30096. Although percentages vary among recent years,
census summaries indicate that about 50% of the breeding population occurs on the upper
coast, 31% on the central coast, and 19% on the lower coast (Texas Colonial Waterbird
Society 1982, Texas Parks and Wildlife Dept. 1992). Estimates
of spoonbill nests in individual colonies in Texas are sparse, however. White et al. (1982) reported 150-200 nests on
dredge-material islands in Nueces Bay at Corpus Christi during 1977-1980, and Oberholser
(1974) referred to five large active colonies in the central coastal area in 1941 but did
not mention nest estimates. SEASONAL OCCURRENCE: Adult spoonbills in full breeding plumage begin congregating at colony sites around mid-March each year (White et al. 1982). Birds are not paired at this time and they loaf in large groups in the vicinity of the nesting area. By mid-April, some pairing has occurred and rudimentary nests are present by late April. Egg laying usually begins during early to mid-May. Data from marked eggs in 29 nests confirmed that laying occurred at the rate of one egg every other day; the time in the nest until hatching is 23 days for the first egg and 22 days for the others (White et al. 1982). Incubation begins the day after the first egg is laid, so the incubation period for each egg is 22 days. On the lower coast, earliest dates for nests with young documented by the TBBAP were 29 May, 4 June, and 6 June. Young spoonbills fledge in early July at about six weeks of age and by early August adults and young begin to disperse from the nesting area. BREEDING HABITAT: Roseate Spoonbills in Texas nest in multi-species colonies in sloughs, marshes, fresh water and brackish lakes, and salt water bays and lagoons (Allen 1942, Oberholser 1974, White et al. 1982). They are among |
the
first to congregate at the colony sites, usually selecting nest sites in or atop low woody
vegetation (rarely on the ground). In Nueces
Bay, spoonbills nested only on dredge-material islands and constructed their nests of
plant material available there or on the nearby shoreline (White et al. 1982). The nest base consisted of large dead twigs of
groundsel tree (Baccharis halimifolia), border paloverde (Cercidium macrum),
and Jerusalem-thorn (Parkinsonia aculeata) loosely fitted together to form a
crude platform. Upon this platform, live and
dead stems of sea ox-eye (Borrichia frutescens), groundsel tree, and grasses were
intertwined into a coarse lining about 5 cm (2 in) deep.
The activities of the birds on the nest eventually formed a wide, shallow
depression in which the eggs were laid. Completed
nests averaged 57 cm (22 in) wide and 11 cm (4 in) deep.
Nest height above ground averaged 24 cm (9 in) atop low vegetation and 71 cm (28
in) in small trees and shrubs. Spoonbills
never built nests on platforms remaining from the previous year. STATUS: According to Allen (1942), Audubon saw thousands
of Roseate Spoonbills along the Texas coast in 1837.
By 1920, a survey party reported only 179 non-breeding birds in June on the
central and lower coast. However, egg
collectors took three clutches in 1921, 1923, and 1924 in Victoria and Refugio counties (Welder Wildlife Foundation Egg
Collection, pers. obs.). With the decline in
plume hunting, spoonbill numbers quickly rebounded. Over
5,000 spoonbills were present on the Texas coast in 1941 (Allen 1942) and the Cooperative
Fish-eating Bird Survey reported 4,470 individuals in 1968 (Oberholser 1974). Surveys for the Texas coast over a recent 20-year
period (1973-1992) suggest that spoonbill numbers during summer range from about 1,400 to
2,500 breeding pairs (2,800 and 5,000 individuals, respectively). Trend data from the Breeding Bird Survey (Sauer et
al. 1997, accessed on 7/13/98) show a slight increase (+1.5%) in spoonbill numbers for the
entire Texas coast, but this trend may reflect normal population fluctuations. Despite
high levels of DDE in some Roseate Spoonbills at Nueces Bay, reproduction (fledglings/eggs
laid) appeared to be good, averaging about 50% (White et al. 1982). Because of a paucity of comparable reproductive
data on this species, it is difficult to assess whether this figure is sufficient to
maintain the population. Since present
numbers appear to be holding steady at about 2300 breeding pairs (Texas Parks and Wildlife
Dept. 1992), nest success probably is adequate and the population is in no immediate
danger of serious decline. Text by Donald H. White (ca. 1998) |
