sign in sign up
<<
Home , Greater scaup, Lesser scaup

Ducks_Vol-II-PartIIb.qxd 12/22/2004 5:28 PM Page 679

Lesser Scaup affinis 679

9.7 eggs (Bengtson 1972b). Incubation, by O alone, of high levels of organochlorine contaminants 26–28 days and starts on completion of clutch. o (Perkins and Barclay 1997) which may have man- usually deserts midway through incubation. Young agement consequences, perhaps even by affecting precocial and nidifugous and, in captivity, weigh thermal properties of as suggested for 38.5 (n ϭ 14). Small crèches sometimes seen. Fledge (Stephenson 1997). Use as biomoni- in 40–45 days by which time juveniles independent. tors of metal contamination advocated in US fed- Hatching success in Finland averaged 77% of eggs eral reserves (Cohen et al. 2000). Legal protection laid over 3 years and 6.5% of young reared to fledg- required for most important areas and control of oil ing, but high variation noted between years (Hildén exploration and transport, both terrestrially in Arc- 1964a). Breeds in captivity sometimes in 1st and tic and by sea elsewhere. legal in 7 coun- usually in 2nd year; not proven in wild. Mean tries of European Union, where 8000 shot annually annual adult mortality of Icelandic estimated at in 1980s (Bertelsen and Simonsen 1986)—the 52% (Boyd 1962); longevity record of BTO ringed majority (Ͼ 80%) in Denmark where seaduck 8 years 5 months (Toms and Clark 1998). hunting in decline. By early 1990s, numbers shot in Denmark c 1000–3000 (Madsen et al. 1996b) and Conservation and threats currently remain at this level. In , winter populations considered to have unfavourable con- Main threat susceptibility to oil pollution when servation status, although threats localized. Not moulting and in winter. In , thought to threatened worldwide (Collar et al. 1994). be less numerous than previously because of oil pollution.Also may be susceptible to accumulation John L. Quinn

Lesser Scaup Aythya affinis PLATE 24

Fuligula affinis Eyton, 1838, Monogr. , wing coverts flecked grey but otherwise as o. Bill p. 157 dark grey; feet and legs as o; eye colour varies with age from olive-brown to olive or brownish yellow Etymology: affinis L. for related or allied, pre- (Trauger 1974). sumably in reference to . Other names: Little , Broadbill (also used MOULT: basic or eclipse plumage of o similar to O for Greater Scaup), Dosgris. French: Petit morillon; but more mottled and lacking face patch. Basic Spanish: Pato boludo chico. plumage of O similar to alternate plumage, but face Variation: no subspecies nor geographical varia- patch less distinct than in alternate. o moults into tion in measurements. basic plumage late June–Aug, with heaviest moult- ing July–Aug, quickly followed by pre-alternate Description moult, completed Sept–Oct. O moults into basic ADULT: dimorphic. o in breeding or alternate plumage early Mar–Apr, and into alternate plumage plumage head black with purplish sheen; neck, Aug–Sept. In both sexes, greatest moult intensity breast and upper mantle black; flanks and belly occurs during wing moult in late summer. white; lower mantle grey flecked and ventral region black. In flight, white wing stripe extends across sec- IMMATURE: before first pre-alternate moult resem- ondaries, primaries greyish brown. Bill slaty blue; bles adult O definitive basic plumage, but white face feet and legs grey with darker webs; eye brilliant yel- patch less clearly defined; scapular feathers plain, low. O fuscous to chocolate brown with white patch and underparts paler and browner. Eyes in o yellow, of varying size at base of bill; upper parts darker, in O brownish or greyish olive. Ducks_Vol-II-PartIIb.qxd 12/22/2004 5:28 PM Page 680

680 Lesser Scaup Aythya affinis

DUCKLING: upperparts dark olive, with inconspicu- white crescent between black breast and grey sides, O ous dorsal pattern; lowerparts pale yellow-buff, darker has white eye-ring and paler face. Tufted has at side and undertail. Head buff-brownish olive with round head with distinct crest and darker back in bright to buff-yellow cheek and throat; dark eyestripe both sexes. O has rounder head, paler throat, well defined in front of eye and contrasting with heavy black nail on bill, and grey wing stripe. often bright yellow lores; post-ocular stripe and pale eye-ring usually well marked. Bill of Lesser Scaup Voice smaller, more slender at base and with smaller nail o generally silent,but gives soft calls during courtship, than Greater Scaup. Bill blackish, iris dark olive or when leading Inciting mate during interactions with brownish grey shifting toward greenish yellow. other conspecifics, and during post-copulatory dis- play; O louder and more vocal. Coughing call, fre- MEASUREMENTS AND WEIGHT: from breeding birds quently uttered by oo in display groups, single in ; see Austin et al. (1998) for summary of whistled whew; Kinked-neck and Head-throw calls of ϭ other locations and periods of life cycle. o (n 40) o faint whee-ooo. O makes repeated low arrr calls while Ϯ Ϯ tail, 47–59 (52.3 0.4); wing, 193–226 (204.8 Inciting during interactions with unpaired oo and Ϯ 1.1); keel, 79.2–89.8 (84.1 0.4); bill, 47–54 other pairs ( Johnsgard 1965a). O gives louder Ϯ Ϯ (50.0 0.3); tarsus, 30.3–37.5 (35.1 0.2). O repeated series of purrr calls during pre-laying and ϭ Ϯ (n 47) tail, 48–56 (52.0 0.3); wing, 184–205 early laying when disturbed by potential mammalian Ϯ Ϯ (195.3 0.6); keel, 76.4–88.3 (82.4 0.4); bill, predator (dog, ); these calls generally given while Ϯ Ϯ 46–54 (49.7 0.2); tarsus, 32.0–36.8 (34.3 0.2). ‘tolling’ to predator (i.e. swimming close with head Weight data from winter (Louisiana), spring (Illinois, and neck extended maximally upwards) or rarely Minnesota), and fall migration (Minnesota), and while circling in flight around predator. southern breeding area (Manitoba); see Austin et al. (1998); o (n ϭ 1718) 546–1156 (maxima: fall staging Range and status [Oct, n ϭ 38] 959.0 Ϯ 17.8; minima: breeding season Breeds in open boreal forest and forest of [May–Jul, n ϭ 40] 721.3 Ϯ 11.3 and winter [ Jan, east to Québec, and south in parkland and n ϭ 28] 721.4 Ϯ 8.8), O (n ϭ 1252) 517–1037 (max- prairie regions of eastern Oregon, Idaho, north Mon- ima: fall staging [Oct, n ϭ 36] 868.1 Ϯ 16.6; minima: tana, North and east South Dakota, and northwest spring staging [Mar, n ϭ 22] 647.5 Ϯ 16.1). Minnesota. Breeding-pair densities in central Canada highest in prairie parkland (north-central Alberta and Field characters southwest Manitoba), and lowest in southeast Alberta Small-bodied (380–430 mm long) dif- prairie grassland and boreal forest (Vermeer 1972). ficult to distinguish in field from larger Greater One of most common breeding wildfowl in boreal Scaup. o has purplish gloss on head and higher pro- forest of interior Alaska,, and Northwest Terri- file in comparison to greenish gloss and low, tories (Trauger 1971, Nudds and Cole 1991). Breed- rounded head profile of Greater Scaup o. Nail at tip ing-pair survey in May (Smith 1995) records largest of upper mandible noticeably and proportionately percentage of breeding scaup (Greater and Lesser smaller in Lesser Scaup; most readily observed in combined), on average, in Boreal Forest Region of field in o. In flight, white wing stripe of Greater Alaska and Canada (68%); smaller percentages Scaup typically extends from secondaries onto inner recorded in Prairie-Parklands of US and Canada 6 primaries, whereas white typically extends only (25%) and Tundra Region of Alaska (7%). Winters across secondaries and cuts off sharply at primaries primarily along Louisiana (Harmon 1962) and of Lesser Scaup. OO cannot easily be separated at Gulf Coasts (Chamberlain 1960), Okee- distance except by wing pattern. chobee, Florida (Turnbull et al. 1986), and Pacific and Ring-necked Duck readily distinguished from Gulf Coasts of Mexico, specifically coastal of Lesser Scaup by peaked head profile, white ring at Tamaulipas and Veracruz and Campeche and Yucatan base of bill, and grey wing stripe; o has dark back, and (Saunders and Saunders 1981, Baldassarre et al. 1989). Ducks_Vol-II-PartIIb.qxd 12/22/2004 5:28 PM Page 681

Lesser Scaup Aythya affinis 681

Largest percentages of wintering scaup recorded, on 1923, Stewart 1975), Minnesota (Roberts 1932) average, in Mississippi (42%) and Atlantic flyways and in Manitoba (Hochbaum 1944). Numbers (41%); smaller percentages in Pacific (10%) and Cen- using migration routes in valleys of Illinois, tral flyways (7%) (Austin et al. 1998).Also common in Indiana, and on Mississippi River declined (Bellrose Pacific Northwest, upper midwest, and upper Atlantic et al. 1979, Mumford and Keller 1984, Korschgen coasts of US. Regular winter visitors farther south 1989). Continental population of Lesser and than other Aythya, to Central and South America and Greater Scaup combined (hereafter referred to sim- (Botero and Rusch 1988); also occurs in ply as scaup), estimated from May Breeding Survey Hawaii and other Caribbean and Pacific islands. (Smith 1995), averaged 5 512 445 Ϯ 147 090 during Occasionally reported in (Bent 1923), 1955–95, with high of 7 996 967 in 1972 and low of Britain (Holian and Forley 1992), and on Canary 4 080 149 in 1993. Lesser Scaup estimated to com- Islands and The Netherlands; presently, 16 confirmed prise 89% of combined continental population of observations in western Palearctic (Clarke et al. 1995). scaup (cf Bellrose 1980, see Austin et al. 1998). Num- No long-term changes in breeding or wintering bers of scaup wintering in US, estimated from Mid- distribution into new range or abandonment of winter Survey (US & Wildlife Service),averaged existing ranges. Breeding populations declined in 1 344 205 Ϯ 77 497 during 1955–95, with high of southern portion of range, e.g. North Dakota (Bent 2 806 249 in 1963 and low of 679 938 in 1983.

Migrant breeding Migrant non-breeding Ducks_Vol-II-PartIIb.qxd 12/22/2004 5:28 PM Page 682

682 Lesser Scaup Aythya affinis

Breeding populations since have declined further to common in such saline habitats than other diving an average of 3 650 000 in 2001–03 (USFWS). except Redhead and Greater Scaup. Distribu- Continental population of breeding scaup tion during migration and winter generally not exhibits no long-term trend (1955–95), despite large closely related to distribution of aquatic plant foods yearly fluctuations. More recently (1975–95), com- as in herbivorous diving ducks. bined continental breeding population declined at Feeds primarily by diving. Diet mainly carnivo- rate of 128 635 birds a year; declines were 44 501 rous and variable, with aquatic invertebrates such as birds per year in Prairie-Parklands and 85 643 birds , , and molluscs dominating. Seeds per year in Boreal Forest, whereas population in and vegetative parts of aquatic plants important in Tundra Region was stable (Austin et al. 1998).Num- certain geographic areas. Diets similar for o and O, bers of scaup wintering in US declined at annual rate and for adult and flying immatures (Bartonek and of 21 409 during 1955–95; declines in Mississippi Murdy 1970, Afton and Hier 1991, Afton et al. Flyway, where few Greater Scaup winter, largely 1991, Custer and Custer 1996). responsible for this negative trend (Austin et al. During spring and summer, adults and ducklings 1998). Continental population probably influenced forage in open water zone of shallow (Ͻ 3m primarily by variation in recruitment rates; annual deep; Dirschl 1969, Hammell 1973, Siegfried survival of OO appears relatively high based on re- 1976b, van Horn 1991). Amphipods, midges sighting of marked adults and ducklings (Afton (Diptera), and leeches (Hirudinea) dominant foods; 1984), and harvest rates relatively low (mean Ͻ 5%). aquatic plant seeds and molluscs important compo- OO exhibit low reproductive rate compared to other nents in some months (Bartonek and Hickey 1969a, ducks, and reproductive success strongly age depend- Dirschl 1969, Bartonek and Murdy 1970,Afton and ent (Trauger 1971, Afton 1984). Recruitment Hier 1991). Diet of juveniles dominated by declines during dry years in Prairie-Parklands due to amphipods (49% total volume), molluscs (39%) and poor nest success and nonbreeding by 1 and 2-year- midges (8%) (Bartonek and Hickey 1969b); old OO (Rogers 1959, 1964, Afton 1984). Recruit- amphipods appear to increase in importance for ment apparently declined recently in Boreal Forest older ducklings (Sudgen 1973). Fledged juveniles (Nudds and Cole 1991), but little known of factors consume primarily amphipods similar to adults col- affecting recruitment in region (Austin et al. 1998). lected in same breeding area. Post-breeding OO in southwest Manitoba consume primarily amphipods, Habitat and general habits leeches, and chironomids. Breeds in association with fresh to moderately Diets during migration generally Ͼ 75% brackish, seasonal and semipermanent wetlands and material. During spring migration through Min- lakes with abundant emergent plants; some use shal- nesota, amphipods comprise 33% (of total dry low river impoundments with deep marsh emer- weight) of diet, with snails (Planorbidae and Valvati- gents. Fall migrants typically found on larger dae) contributing another 32% (Afton et al. 1991). semipermanent and permanent wetlands and lakes, During fall migration through Minnesota,amphipods such as along (Bookhout et al. 1989) and comprise 55% (of total dry weight) of diet; snails and large impounded portions of (Ͼ 3000 ha) in fingernail clams Sphaerium together comprise 15%, Minnesota, Wisconsin and Iowa (Korschgen 1989); and 3 species of fish another 10% (Afton et al. 1991). along coasts, found on large wetlands, lakes, reser- Along Mississippi River in Iowa, fingernail clams voirs, and fresh to brackish . Spring migrants dominate (Ͼ 95% of food items; Thompson 1973). use smaller wetlands and marshes. Most moulting While migrating through and Lake St. concentrations found on large boreal forest lakes. Clair,diet is 92% Zebra (aggregate % number; Wintering birds mainly use lakes, reservoirs, and Custer and Custer 1996) introduced from central fresh to brackish coastal bays and estuaries of south Europe and now at high densities (Leach 1993). In Atlantic and Gulf Coasts (Chabreck et al. 1989, Klamath Basin of northern California, chironomids Johnson and Montalbano 1989). During severe (44% by volume) and ostracods (18%) form major weather may move to more saline waters; more portion of diet (Gammonley and Heitmeyer 1990). Ducks_Vol-II-PartIIb.qxd 12/22/2004 5:28 PM Page 683

Lesser Scaup Aythya affinis 683

During winter, feeds mainly on open waters of Displays and breeding behaviour Gulf of Mexico and on coastal bays, marshes, and Monogamous, but mate changes common on inland lakes of southeastern US. Specific components breeding areas prior to egg-laying. Mate switches of winter food vary geographically and often reflect occur after extensive fighting among oo.Trios (2 oo local abundance. In most coastal areas, diet domi- and O; novice o and pair of Hochbaum 1944; see nated by molluscs and benthic invertebrates (Har- also Trauger 1971) result when displaced mate fol- mon 1962, Hoppe et al. 1986, Jones and Drobney lows his former O and new mate for extended peri- 1986,Afton et al. 1991). In contrast, along Columbia ods. Performance of displays, vocalizations, and River in Oregon and Washington, diet mostly vege- agonistic behaviour similar to other Aythya ( Johns- tative parts of Elodea and Potamogeton, and plant seeds gard 1965a). from 6 aquatic species (Thompson et al. 1988). On breeding grounds, paired oo Turn-back-of- Migratory throughout range, staging Sept–Oct head to Inciting mates (i.e. OO perform Neck-stretch- and arriving on winter areas Nov–Dec, among lat- ing and Chin-lifting) in interactions with other pairs est migrants in North America. Depart winter areas and unmated oo ( Johnsgard 1965a). Cough most late Feb–Mar, arriving on breeding grounds May. common o display, wing and tail flicked while giving Moult migration by oo but participation by O vari- whew whistle. Kinked-neck call given with little head able and little studied. movement. Head-throw preceded by preliminary Feeding and resting common behaviours during Head-shake and associated with whee-ooo call. While spring migration; time-budgets of sexes similar and performing Turn-back-of-Head towards Inciting O, time spent feeding greater during day than night. head feathers of o depressed to produce low profile. During pre-laying and laying, OO spend more time Preen-behind-wing frequent, often mutual with feeding than mates for 1st nest and re-nests, and mate.Paired oo frequently direct forced copulations at during day and night; oo spend more time alert fertilizable, often older OO (Afton 1985). than O during same periods. oo spend considerable On southern breeding areas, mid Apr-early June, time alert during early incubation when mates are sex ratios average 60–68% o (Ellig 1955, Bellrose on nests and while with their mates during incuba- et al. 1961). Segregation by sex generally not observed tion recesses. Feeding and comfort movements on wintering areas (Bergan and Smith 1989); how- most frequent behaviour of O during incubation ever, greater proportion of adult oo occurs in flocks recesses. Time spent alert by brood hens high, on Gulf of Mexico than in coastal Louisiana marshes. declining as ducklings grow older; time spent in locomotion by brood hens increases with duckling age, whereas other behaviours do not vary much. Breeding and life cycle Premoulting adults spend most time resting, Pairbond formed Mar–Apr during spring migra- feeding, locomoting, and in comfort movements. tion and maintained until mid or late incubation. Feeding, resting, and comfort behaviour comprise One of latest North American ducks to pair, with largest time of moulting o and O. During fall most pairing occurring quickly during late spring migration, feeding and resting are most common migration (Apr-early May). Less than 10% paired behaviours; time spent feeding by juveniles greater Dec–Jan, 12–17% paired Feb–Mar, and 56% than that of adults of both sexes (Austin et al. 1998). Mar–Apr (Weller 1965); 60% paired in northwest Breeding pairs have relatively small, highly over- Minnesota late Apr (Austin et al. 1998), 68% of oo lapping home ranges (Afton 1983, 1984) and share and 99.8% of OO paired by early May on Delta loafing sites. Pre-nesting pairs may tolerate other Marsh, Manitoba (Siegfried 1974c); all OO paired by individuals or pairs within 1–2 m (Hammell 1973), mid May in southwest Manitoba (Austin et al. but paired oo more aggressive and maintain greater 1998).Adult OO philopatric to natal areas—66% of inter-pair distances when mates laying. Individuals 68 marked adult OO in Manitoba (Afton in Johnson maintain greater distances between conspecifics on and Grier 1988), and 20% of 330 banded OO in wintering areas than on major northern fall migra- Northwest Territories, returned to breed (Trauger tion areas. 1971). Fidelity by o low (6–9%; Trauger 1971, Ducks_Vol-II-PartIIb.qxd 12/22/2004 5:28 PM Page 684

684 Lesser Scaup Aythya affinis

Afton in Johnson and Grier 1988). Fidelity to natal 1979). Nest success in Prairie-Parklands averaged area by yearlings higher for O than o (12% v 0% of 29.5% (n ϭ 613) (Kalmbach 1937, Kiel 1953, Smith marked yearlings, respectively,banded in Northwest 1953, 1955, Rogers 1964, Vermeer 1968, Hammell Territories; Trauger 1971; 49% v 4% in Manitoba; 1973, Hines 1977, Sankowski and Joynt 1992, North- Afton in Johnson and Grier 1988). ern Prairie Wildlife Research Center unpubl. data). Both o and O can breed at 1 year of age, but some In Boreal Forest, nest success averaged 29.4% in oo probably do not because of excess in population. Alaska (n ϭ 29) and 67.7% in Northwest Territories Most nonbreeding OO are 1 and 2 years old (Afton (n ϭ 21). Nest success low in Washington (10%, 1984). Most pairs breed in wet years but proportion n ϭ 56) (Gehrman 1951). On islands in Prairies, nest of nonbreeding pairs varies with O age and water success averaged 31.0% (n ϭ 565) (Leitch 1952, Keith conditions (Rogers 1964, Afton 1984). OO 3 years 1961, Long 1970, Hammell 1973, Brown 1987). Pro- and older make one breeding attempt a year under portion of OO re-nesting after loss of 1st nest does not most conditions (Afton 1984). Nesting more syn- vary with age or among years (overall mean of 16.4%, chronous over large geographic range than in other n ϭ 73) but tends to be lower in year-olds and to ducks. Peak nesting period in most areas during June increase with improving water conditions (Afton (Murdy 1964,Vermeer 1968, Hammell 1973, Hines 1984). 1977, Stewart 1975, Afton 1984). Mean date of nest Most unsuccessful nests lost to American Mink, initiation of first nests later for year-old OO than for , , M. mephitis, Common older OO (20 June v 12–15 June) (Afton 1984). Most American Crow, Ring-billed Larus delawarensis and nests located on or near land in tall vegetative cover, California , and American Badger (Keith sometimes in upland far from water. In Prairie Pot- 1961,Vermeer 1968, Hammell 1973, Afton 1984). hole Region, usually situated in tall vegetation in In agricultural areas, some nests lost to farming wet-meadow zones of prairie and lakes, native operations (Afton 1984). Young smaller than prairie tracts, hayfields, along ditch banks, on islands, Greater Scaup and ducklings of same age. and occasionally in growing grain.In Northwest Ter- Day-old ducklings in Alberta averaged 29.8 Ϯ 0.22 ritories, nests typically concealed in dense, tussocky (26.0–34.2) (n ϭ 51 from 6 broods) (Nelson 1993). sedge, within 1 m of open water, with abundant Rectrices and side feathers come in first, followed lateral and overhead cover. Commonly nests by scapular area, breast and belly, rump and back, on islands, at times at high densities (Long 1970,Ver- head and neck, and lastly mantle; remiges emerge c meer 1968, Brown 1987). Day 29–33. Shafts of primaries begin to clear c Day Eggs pale olive or greenish buff to dark olive- 49 (Lightbody and Ankney 1984); flight attained c buff, smooth and slightly glossy; elliptical to nearly Day 47–61 (Gollop and Marshall 1954, Schneider oval; 57.0 ϫ 39.4 (n ϭ 145) (Gehrman 1951); clutch 1965). Hen attends brood 2–5 weeks, usually aban- mostly 8–10 (6–14) eggs, in late nests (most likely re- dons as young fly. Crèching, or amalgamation of nests) smaller than early nests (10.2–10.6 for nests ini- several broods, occurs frequently in areas with high tiated Ͻ 30 June v 8.5 for later nests in southern nest success, relatively synchronous hatching, high Alberta; Keith 1961). Eggs lost to infertility or brood densities and limited suitable habitat (Hines embryo death Ͻ 10% (Miller and Collins 1954,Ver- 1977,Afton 1993).Amalgamated broods often con- meer 1968). Nest success varies among years, areas sist of several age classes and may include Ͼ 100 and habitats, largely due to differential predation. In ducklings and up to 6 OO; typically 15–40 duck- Prairie-Grasslands, nest success ranged 8.2% (Giroux lings with 2–3 OO (Hines 1977, Campbell et al. 1981a) to 90% (Aufforth et al. 1990) and averaged 1990). 37.3% (n ϭ 1185) (Ellig 1955, Keith 1961, Stoudt Some 67.5 Ϯ 4.9% of ducklings within broods 1971,Giroux 1981a,Holm 1984,Aufforth et al. 1990, survive 3 weeks (n ϭ 39 broods) (Afton 1984). Northern Prairie Wildlife Research Center unpubl. Annual estimated mortality rate for birds banded data; all nest success values expressed as Mayfield nest during summer before 1962 averaged 71% of success or Discrete Green estimator, see Johnson immatures and 32% for adult oo (Smith 1963). Ducks_Vol-II-PartIIb.qxd 12/22/2004 5:28 PM Page 685

Lesser Scaup Aythya affinis 685

Annual estimated mortality for those banded during Conditions along fall migration routes and on winter and early spring (1941–62) averaged 47.5% wintering grounds have changed greatly over past for adult oo and 53.7% for adult OO. Overall appar- 50 years, mainly due to human activity affecting water ent survival of yearling and after-2nd-year OO was quality and food resources. Most significant are recent 0.57 on Manitoba and breeding sites explosion of Zebra in Great Lakes and major (Rotella et al. 2003). rivers, which provide enhanced food resources for migrating and wintering scaup, and industrial thermal Conservation and threats pollution, allowing scaup to winter farther north. How these changes have affected migration, hunting Highly regarded game species in north-central and pressure and mortality,and winter condition of Lesser eastern US and in central Canada; less preferred Scaup poorly understood.Investigations need to com- elsewhere. US harvest averaged 341 523 Ϯ 29 523 pare fall and winter survival rates between those Lesser for 1961–94, with high of 686 752 in 1977 and low Scaup that now migrate through Great Lakes v more of 93 327 in 1962 (Austin et al. 1998). Largest per- traditional river migration routes. Comparisons of centages taken in Mississippi Flyway (62%), prima- overwinter survival and prebreeding condition of rily in Minnesota, Louisiana, and Michigan; smaller scaup that winter in Great Lakes and other northern percentages in Central (16%), Atlantic (13%) and sites v traditional southern sites also needed to assess Pacific Flyway (9%). Harvest declined in all flyways cross-seasonal influences. since late 1970s, primarily due to decreasing num- Habitat degradation important in altering bers of scaup and hunters, and more restrictive migration routes and use of breeding and wintering hunting regulations since 1988. areas of Lesser Scaup, particularly in Illinois and Investigations into life history and ecology limited Mississippi River Valleys. Declines probably due to by remoteness of core breeding area in northern disappearance of food resources such as fingernail Boreal Forests and northern Parklands; most knowl- clams whose demise coincided with increased pol- edge based on studies in southern portion of breed- lution, sedimentation, and altered water levels on ing range. Further information needed on factors Illinois River (Mills et al. 1966, Bellrose et al. 1979). influencing recruitment and survival rates, particu- Disturbance to migrant flocks also may be impor- larly in northern regions where populations declin- tant (Korschgen et al. 1985, Havera et al. 1992a). ing and information least available. Investigations also Wetlands along Lake Erie and Detroit River have needed into relationships of wetland and weather suffered siltation, landfill, exotic plant introduction, conditions during spring migration to subsequent and water-level controls (Bookhout et al. 1989). recruitment; specifically,does drought in prairie pot- Drainage of wetlands and conversion to agriculture hole region during spring migration affect nutrient in Prairie Grassland and Parkland regions have reserves, migration, and annual recruitment? decreased quality and quantity of habitat used dur- Knowledge of population size and trends con- ing spring migration and breeding (Higgins 1977, founded by inability to separate Lesser from Rakowski and Chabot 1983, Turner et al. 1987). Greater Scaup in breeding and wintering survey Habitat degradation and loss from draining, dredg- data, and by potential biases in May Breeding Sur- ing, levee construction, and altered water flow and vey (Austin et al. 1998). Separate estimates of Lesser salinity of concern in southern coastal marshes of and Greater Scaup in May Breeding Survey and Louisiana and Florida (Chabreck et al. 1989, John- Midwinter Survey needed to clarify population sta- son and Montalbano 1989). In Boreal Forest tus of both species. Potential biases in May Breed- Region of Northwest Territories, extensive new ing Survey (e.g. possible double-counting during mining developments threaten breeding habitat. cold late springs) need investigation and correction. Similarly, Midwinter surveys need to be improved Jane E.Austin, Christine M. Custer for coverage and accuracy. and Alan D.Afton