Добірка наукової літератури з теми "Northern shoveler"

AbstractWe collected unincubated eggs from wild Mallard (Anas platyrhynchos), Gadwall (A. strepera), Blue-winged Teal (A. discors), and Northern Shoveler (A. clypeata) nests and artificially incubated them at 37.5°C. Average incubation lengths of Mallard, Gadwall, and Northern Shoveler eggs did not differ from their wild-nesting counterparts, but artificially incubated Blue-winged Teal eggs required an additional 1.7 days to hatch, suggesting that wild-nesting teal incubated more effectively. A small sample of Mallard, Gadwall, and Northern Shoveler eggs artificially incubated at 38.3°C hatched 1 day sooner, indicating that incubation temperature affected incubation length. Mean incubation length of Blue-winged Teal declined by 1 day for each 11-day delay in nesting, but we found no such seasonal decline among Mallards, Gadwalls, or Northern Shovelers. There is no obvious explanation for the seasonal reduction in incubation length for Blue-winged Teal eggs incubated in a constant environment, and the phenomenon deserves further study.

Pair formation in ducks is thought to be influenced by the acquisition of breeding plumage, the occurrence of courtship display, or both. We examined the frequency of pair formation in Mallard (Anas platyrhynchos), Green-winged Teal (Anas crecca carolinensis), and Northern Shoveler (Spatula clypeata) in the central valley of California in relation to the frequencies of male attainment of breeding plumage and courtship display. Predictions related to two hypotheses are: (1) the timing of pair formation is directly related to the attainment of breeding (definitive alternate) plumage by males, and (2) frequencies of courtship display are highest during pair formation. Most female Mallard were paired by the end of October, with >80% in pairs by early December. Of Northern Shoveler, 90% were paired by early January and 90% of female Green-winged Teal were paired by early February. The highest rates of courtship display by Mallard were observed during October through November, by Northern Shoveler in November, and by Green-winged Teal in November through January. Courtship display was, therefore, relatively frequent at the same time as pair formation for all three species. Northern Shoveler spent less time in courtship display than the other two species. Most (90%) male Mallard had acquired alternate plumage by mid-November, Northern Shoveler by early February, and Green-winged Teal by mid-December. Thus, timing of pair formation coincided with timing of attainment of breeding plumage in Mallard and Green-winged Teal but not Northern Shoveler.

Breeding events of a waterbird species outside of their normal breeding grounds could be important to address how population changes on wintering areas are impacted by changes elsewhere in the birds’ annual cycle. In this note we confirm the first breeding record of Northern Shoveler Spatula clypeata in Algeria. The breeding site was a saline lake, Sebkhet El-mahmel, located 180 km from the Mediterranean Sea and subject to a semi-arid climate. The area was visited on 16 June 2019 and the species was confirmed as a pair of Northern Shoveler accompanied by eight juveniles. The Northern Shoveler is an unmistakable waterbird species in the northern hemisphere due to its distinctive bill. The female and her juveniles looked healthy and they spent almost the entire daytime foraging and swimming.

This study examined foraging strategies in male Northern Shovelers (Anas clypeata) and Blue-winged Teal (Anas discors). Differences in time–activity budgets and esophageal contents between the two species indicated major differences in the degree of foraging specialization. Preflightless male Northern Shovelers spent 84.2% of time foraging, with dabbling in the water column as the principal foraging mode (83.4%), while postflightless male shovelers spent 81.6% of time foraging (78.7% dabbling). Preflightless male Blue-winged Teal spent 68.6% of time foraging, with dabbling in mud (32.5%) and picking in vegetation (29.4%) as the two principal modes, whereas postflightless male bluewings spent 85.9% of time foraging (dabbling in mud 40.6%, and picking 34.2%). Most male Northern Shoveler food items were cladocerans (85.5%) or chironomid pupae (12.9%); this was related to the specialized foraging method employed by shovelers. Male Blue-winged Teal food items were principally gastropods (44.3%), culicids (29.2%), seeds and vegetation (15.5%), and chironomids (5.6%), which corresponded to the plastic feeding behaviors of bluewings. Examination of esophageal items revealed that male Northern Shovelers did little feeding during the summer flightless period, while male Blue-winged Teal fed throughout the period.

Abstract We investigated patterns and causes of variation in clutch sizes in a guild of five species of temperate-nesting dabbling ducks (Mallard [Anas platyrhynchos], Northern Pintail [“pintail,” A. acuta], Gadwall [A. strepera], Blue-winged Teal [“teal,” A. discors], and Northern Shoveler [“shoveler,” A. clypeata]) during 1993-1995 in the Prairie Pothole Region of midcontinental North America. Clutch sizes (mean ± SE) were largest for teal (10.80 ± 0.03), followed in descending order by those of shoveler (10.31 ± 0.05), Gadwall (9.92 ± 0.04), Mallard (8.91 ± 0.04), and pintail (7.66 ± 0.06). In Mallard, pintail, and shoveler, predicted clutch sizes at onset of nesting exhibited minimal variation. Clutch sizes of Gadwall and teal displayed statistically significant variation among years at onset of nesting; pintail clutch sizes showed significant variation late in the nesting season. Clutch sizes declined seasonally in all species. Declines in clutch sizes of teal and shoveler were approximately linear; whereas clutch sizes of Mallard, pintail, and Gadwall usually declined at progressively decreasing rates. Linear declines in teal and shoveler clutches suggest that those species experienced greater difficulty securing lipids for egg production late in the nesting season than did Mallard, pintail, and Gadwall. That disparity may result because egg-laying female teal and shoveler feed almost exclusively on animal foods, which are primarily protein; whereas female Mallard, pintail, and Gadwall consume more carbohydrate-rich plant foods. Our findings, when examined in context with existing information, suggest that interspecific variation in clutch sizes results from innate differences in several traits—including body size, diet, timing of lipid acquisition, and nesting—all of which can affect the amount of lipid available for egg production. Temperate-nesting dabbling ducks have evolved traits that facilitate laying of large clutches early in the nesting season, because risk of mortality is lower among early-hatched young. Annual differences in clutch sizes of all five species were not significant when effects of annual variation in nest-initiation dates were accounted for, reflecting the key role of environmental influences on intraspecific variation in clutch sizes among years.

AbstractI compared nesting intervals during three consecutive years in five species of temperate-nesting dabbling ducks (Mallard [Anas platyrhynchos], Northern Pintail [Anas acuta], Northern Shoveler [Anas clypeata], Blue-winged Teal [Anas discors], Gadwall [Anas strepera]) and assessed whether differences existed in timing of refractoriness. Most nesting by females of all five species ended by the summer solstice. Nesting ended earliest for Northern Shovelers and Northern Pintails and latest for Gadwalls. Some Mallards, Blue-winged Teal, and Gadwalls continued to nest into mid- and late summer, whereas Northern Shovelers and Northern Pintails did not. Mallards, Blue-winged Teal, and Gadwalls accounted for 99% (81 of 82) of flightless broods resulting from nests initiated during mid- or late summer in North Dakota and 98% (58 of 59) of flightless juveniles shot on or after 1 October by a random sample of duck hunters from across the United States. Early cessation of breeding by Northern Shovelers may have evolved in response to the species' limited flexibility in diet. Photorefractory mechanisms that limit most breeding to spring presumably evolved in response to severe constraints on reproductive success when nesting continued through summer (e.g. mortality of late-hatched young and molting females due to low temperatures). Interspecific differences in photosensitivity may account for variation in timing of cessation of nesting in late spring, but controlled experiments are needed to assess the possible role of non-photic influences. My results suggest that the refractory mechanisms controlling length of the breeding season in temperate-nesting dabbling ducks are more varied and complex than previously thought, with non-photic influences (e.g. water conditions, food availability, food quality) having a larger role than indicated by earlier research.

The objective of this study was to evaluate the characteristics of the carcass, physicochemical properties as well as nutritional composition in breast and leg meat (with skin) of two different genotypes of wild birds namely: pintail (Anas acuta) and shoveler (Spatula clypeata) with regard to sex effect. The study involved forty-eight birds, 24 pintail and 24 shovelers (1:1 sex ratio) harvested during the hunting season (in September and November 2020) in lake Nasser from the Gerf-Hussein region, south Aswan Government. After the slaughter and dissection. PH, WHC and color coordinates of the breast and leg muscles were specified after 24 h of slaughter. After the dissection, breast and leg meats minced with their skin were sampled to determine cross composition, some minerals, amino acids profiles. The studied birds showed significant differences in body weight (BW), carcass weight, dressing percentage and percentages of neck and gizzard. Genotype affected the redness (a*), yellowness (b*), moisture, fat, ash and energy value of breast muscles, and also pH24, lightness (L*), redness (a*), moisture, fat, ash and energy value of leg muscles. Regardless of genotype, males showed higher body weight, carcass weight, as well as breast and leg cuts weight compared to females. The shovelers had a higher content of K, Mg, Ca, Fe and Co in breast and leg muscles compared to the pintail. While Pb and Cd exceeded maximum admissible levels which are recommended by European common regulation. Cd was detected only in breast and leg muscles from pintail. The essential amino acid content ranged from 39.73-44.45 g/100 g protein in pintails against 41.46-44.94 g/100 g protein in shovelers.

Abstract We used microprocessor data loggers to document patterns of nest attendance during the laying stage and to quantify temperatures of dummy eggs during laying for Mallard (Anas platyrhynchos), Blue-winged Teal (A. discors), Northern Shoveler (A. clypeata), Northern Pintail (A. acuta), Gadwall (A. strepera), Green-winged Teal (A. crecca), American Wigeon (A. americana), and Lesser Scaup (Aythya affinis) nesting in southern Manitoba in 1994 and in northeastern North Dakota in 1995–1997 and 2000–2002. Females of all species increased the time they spent on the nest as laying progressed, but species differed in their pattern of increased attendance. Female Blue-winged Teal and Northern Shoveler that laid smaller clutches increased the time they spent on the nest more rapidly than conspecifics that laid larger clutches, but large- and small-clutch conspecifics had similar attendance at the end of the laying period. Attendance during laying was not influenced by low ambient temperature, precipitation, or nest initiation date. For all species combined, maximum egg temperatures increased as laying progressed. Eggs were heated to temperatures sufficient for embryonic development as early as the day that the second egg was laid. Our findings contradict the prevailing paradigm that incubation in waterfowl begins after clutch completion and raise questions about how hatching synchrony is achieved. We relate our findings to two hypotheses (nutrient limitation and viability–predation) that have been proposed to explain the limits to clutch size in ducks.

Both members of pairs of mallards (Anas platyrhynchos), northern pintails (Anas acuta), northern shovelers (Anas clypeata), and American wigeon (Anas americana) were collected early in the pairing periods in fall and during spring migration (several months after most birds were paired) to provide insights into whether (i) assortative mating occurs; (ii) body condition changes synchronously among pair members; and (iii) characteristics of selected individuals ultimately confer advantages in survival and recruitment. Both members in 19 of 21 mallard, 16 of 16 pintail, 14 of 14 shoveler, and 14 of 15 wigeon pairs were adults. The predominance of adults in pairs in fall indicates that adults pair earlier than juveniles and suggests at least some assortative mating in relation to age. Generally, body and nutrient reserve masses of males and females within a pair were correlated for all species in both fall and spring, suggesting that individuals tend to form pairs with others of relatively similar body condition, and also that once paired, the body condition of the two members tends to change at the same time. In contrast to body condition, measures of structural size of pair members were not correlated. Field data suggest that older and heavier ducks have greater survival and reproductive potential than young, lighter ducks; consequently, selection of old and heavy mates is probably evolutionarily advantageous.