Shooting And Trapping
A small proportion of the pintail population is harvested annually in sport and subsistence harvest (Miller and Duncan 1999). Annual sport harvest in the U.S. occurs primarily in California, Texas, and Louisiana and varies annually with population size and harvest regulations (Miller and Duncan 1999). Annual sport harvest in the U. S. averaged 1.1 million in 1961–1978, 927,000 in 1979–1984; declined to 330,000 in 1985–1994 with implementation of harvest restrictions in 1985, but increased to 481,000 in 1995-2004 and 519,000 in 2005-2010 (U.S. Fish and Wildl. Serv. unpubl. data). Sport harvest in Canada averaged 199,000 in 1972-1978, 121,000 in 1979-1984, and 54,000 in 1985-2010; before 1985 was about 70,000 annually (Legris and Levesque 1991b), currently is about 35,000 (U.S. Fish and Wildl. Serv. unpubl. data)) and <10,000 in Mexico during 1987-1992 (Kramer 1995, G. W. Kramer pers. comm.).
Annual sport harvest rate of adult females ranged from 5-12% and was <3% of the continental population during 1960-1970, 5-7% during 1971-1984, and <2-5% during 1985-1998 (M. Runge from data in Sheaffer et al. 1999 [Figure 3 in Miller et al. 2003; U. S. Fish and Wildlife Service and Canadian Wildlife Service 1992) and <10% of annual mortality for adult females is attributable to hunting (U.S. Fish and Wildl. Serv. unpubl. data); current harvest rate is assumed to have no effect on the continental population.
Sport harvest in the U.S. is currently managed using an adaptive approach to identify optimal regulatory strategies that maximize long-term cumulative harvest (U.S Fish and Wildlife Service 2010). There is substantial spring, summer, and fall subsistence harvest of Northern Pintails and their eggs by Canadian Native Americans Macaulay and Boag 1974, Finney 1990, Wendt and Dickson 1994) and Alaskan Eskimos with ( subsistence harvest of waterfowl in Canada equaling about 5%, and in Alaska about 1% , of overall sport harvest in North America [U. S. Fish and Wildlife Service 2012)Macaulay and Boag 1974). Reported annual subsistence harvest by Alaskan Eskimos was accounted for 6,893–17,450 adults and 85–1,100 eggs annually during 1985–1993 (U.S. Fish and Wildl. Serv. unpubl. data) and averaged 22,357 adults and 2,015 eggs in 1995-2000 (Alaska Migratory Bird Co-Management Council. 2012); effect on nest productivity, recruitment, and population size is unknown.
Pesticides And Other Contaminants
Mercury, obtained from cereal grain treated with methyl mercury fungicides, was detected pintails nesting in N. Dakota (1969–1970) at levels that could reduce hatching rates (0.055–9.512 parts per million [ppm] wet weight) but not cause death (Krapu et al. 1973); this chemical is no longer in use. Carbofuran poisoning occurs periodically in conjunction with rice farming in California (Littrell 1988). Organochlorine contamination of Northern Pintails was recorded below acutely or chronically lethal levels (<1 ppm wet weight) in California (1980–1981, Ohlendorf and Miller 1984) and Mexico (1981–1982, Mora et al. 1987), but residues were higher later in winter via accumulation. In Alberta, ducklings had higher concentrations of total DDT and dieldrin than other species, but concentrations declined as ducklings grew (Charnetski 1976). Selenium from agricultural drainwater used to manage wetlands in the San Joaquin Valley, CA, has contaminated wintering Northern Pintails, and liver concentrations high enough to cause reproductive impairment that were detected in late 1980s (Paveglio et al. 1992) have since declined but still remain above background levels (Paveglio and Kilbride 2007).
Ingestion Of Plastics, Lead, Etc.
Nearly 9% of gizzards from hunter-shot Northern Pintails in North America contained lead pellets during 1938–1953—the highest percentage for any dabbling duck (Bellrose 1959). Of Northern Pintails picked up throughout the U.S. and successfully diagnosed, lead poisoning accounted for 11% (n = 686; National Wildlife Health Center, Natl. Biol. Serv. unpubl. records 1984–1994). Lead poisoning has caused large die-offs at times (Sanderson and Bellrose 1986), but Deuel (Deuel 1985) found no difference in band recovery rates for lead-dosed and control Northern Pintails banded after the hunting season in California, suggesting late-winter/spring diets, high in protein and calcium, may counteract effects of lead (Sanderson and Bellrose 1986).
Conversion to nontoxic shot for waterfowl hunting starting in 1976, with a complete ban of lead shot use for waterfowl hunting in U.S. in 1991 (Samuel and Bowers 2000) and in Canada in 1999 (Anderson et al. 2000), has significantly reduced lead ingestion in Northern Pintails in U.S. (Anderson et al. 1987b); although ingestion still occurs, especially in wetlands underlain by hardpan clay (Thomas et al. 2001) .
Collisions With Stationary/Moving Structure Or Objects
Collisions with fences and power and telephone lines documented in Montana (264 birds in 2 yr; Malcolm 1982), Prairie Pothole Region Coues 1874a, Richkus et al. 2005, Natl. Biol. Serv. unpubl. data), and California (Fleskes et al. 2002.). In s. Alberta, 4 of 20 radio-marked nest trapped females were killed by apparently colliding with power lines (Guyn 2000). In prairies, killed by vehicles (Sargeant 1981); nesting hens killed by farm machinery (Natl. Biol. Serv. unpubl. data).
Degradation Of Habitat: Breeding And Wintering
Drainage of wetlands and agricultural alterations of prairie landscapes in s. Canada and n.-central U.S. are continuing problems. Upland habitat changes in the PPR of Alberta, Saskatchewan, Manitoba, North Dakota and South Dakota – the primary breeding ground for pintails (Bellrose 1980, Miller and Duncan 1999) - generally have been considered responsible for the weakened relationship between wetland numbers counts and pintail numbers (Bethke and Nudds 1995, Miller 1996, Miller and Duncan 1999). Specifically, loss and fragmentation of suitable breeding habitat due to changes in agriculture on the prairies (Trauger and Stoudt 1978, Bethke and Nudds 1995, Miller 1996) and an associated reduction in nest success (Greenwood et al. 1995, Beauchamp et al. 1996) often are hypothesized as reasons for suppressed pintail numbers in recent decades. There is also evidence that changes in cropping practices on the Canadian prairies, specifically the conversion of summer fallow to annual cropping, has substantially degraded the capacity of the prairie and parkland landscapes for pintail reproduction (Podruzny et al. 2002). Alaska nesting habitats are largely intact, but oil contamination may be a potential problem. Migratory habitat in Illinois River Valley has been drastically altered (Bellrose et al. 1979). In California, ducks on winter wetlands compete against agricultural and urban interests for limited water and space as human population grows (MRM). Winter habitats associated with agricultural regions in Sacramento and San Joaquin Valleys and in San Francisco Bay region have potential for chemical contamination (Ohlendorf and Miller 1984). Conditions on wintering areas in Mexico are stable on coastal marshes, but foraging areas are subject to varying extent of rice acreage annually (Migoya and Baldassarre 1993).
Disturbance At Nest And Roost Sites
No data for nest sites. At Sacramento National Wildlife Refuge, CA, during fall and winter, human disturbances (vehicles, adjacent hunting, refuge-staff activities, etc.) accounted for ≤68% of disturbances to roosting Northern Pintails, and avian/mammalian predators accounted for the remainder (Wolder 1993).
In a study done in s. Alberta and s. Saskatchewan, approximately 25% of non-abandonment nest failures in spring-seeded cropland were the result of spring tillage operations, with the balance due to depredation (J. Devries, pers.com, Ducks Unlimited Canada), a result similar to previous estimates (17% Greenwood et al. 1995; 20 – 33% Richkus 2002; 18% Devries et al. 2008). Similar results have been found for pintails nesting in hayland, where 16% of non-abandonment pintail nest failures were the result of haying operations (J. Devries, pers.com, Ducks Unlimited Canada). Nests in croplands are particularly susceptible to loss from farming activities; 17% of unsuccessful nests (n = 782) were lost to farming activities in Alberta, 1982–1985 (Greenwood et al. 1995a). Radio-tagging has potential to affect behavior, nesting, and mortality (Guyn and Clark 1999).