2007 NORTHEASTERN NATURALIST 14(3):375–386 The Timing of Waterfowl Arrival and Dispersion During Spring Migration in Labrador Keith G. Chaulk1,* and Bruce Turner2 Abstract - Weekly aerial surveys were conducted in central Labrador during the spring staging period (27 April to 29 May, 2000), and the relative abundance of waterfowl was documented. Anas rupribes (American Black Duck) and Bucephala clangula (Common Goldeneye) were among the first species to arrive, while peak waterfowl diversity occurred on the latest survey date. Overall, Branta canadensis (Canada Geese) were the most abundant species, followed by American Black Duck and Anas crecca (Green-winged Teal). As expected, the relative abundance of these species varied by date and region. By the time of the last survey on 29 May, average flock size had decreased for most species, most likely corresponding with the start of breeding and nest initiation. Our findings could be useful as baseline information for future studies of climate change, may have implications for the management of the aboriginal spring hunt, and also might be used to mitigate the effects of military flying activity. Introduction Understanding spatial and temporal patterns in the distribution and abundance of animals is important because these patterns can be indicators of ecosystem change. Migratory birds in the high latitudes are particularly interesting in this respect because of the apparent regularity and extent of their annual movements (Gwinner 1996). Many migratory bird species start their migration on or around the same time each year (Coppack and Both 2002). However, recent evidence has demonstrated that large-scale processes like climate change can influence the timing of migration (Coppack and Both 2002, Hüppop and Hüppop 2003) and breeding (Both and Visser 2001, Brown et al. 1999, Crick and Sparks 1999, Crick et al. 1997). While many waterfowl demonstrate fidelity to breeding sites (Eadie and Gauthier 1985, Seymour 1991, Zicus and Hennes 1989), or wintering sites (Hestbeck et al. 1991, Lincoln 1934), and in some cases to staging areas (Afton and Hier 1987), it is not clear if all species demonstrate fidelity to staging areas (Moison et al. 1967). Regardless, spring migration is an important period during waterfowl life history, and staging areas provide waterfowl with the resources needed to maintain, restore, or increase the energy reserves to meet the demands of migration and reproduction. Different strategies are evident across different species (Alisauskas and Ankney 1992, Gauthier et al. 1984, Krapu and Rienecke 1992, McLandress and Ravelling 1981, Thomas 1982). In this paper, we look at temporal and spatial patterns of waterfowl on staging habitats during the spring period in 1Canadian Wildlife Service, Goose Bay, NL, A0P 1C0, Canada. 2Canadian Wildlife Service, Mt. Pearl, NL, A1N 4T3, Canada. *Corresponding author - keith.chaulk@ec.gc.ca. 376 Northeastern Naturalist Vol. 14, No. 3 Labrador, a sub-arctic region in eastern Canada. This information may have use for future population-monitoring surveys, and/or comparing the effects of climate change on waterfowl migration patterns in this sub-arctic region. Our findings may have implications for the management of the aboriginal spring hunt, and also be might be used to mitigate the effects of military flying activities in Labrador. Study Area The study area was divided into three general regions centered on Goose Bay, NL (Fig. 1). The southern region contained survey sites with Figure 1. Study area of spring-staging surveys conducted in Labrador from 27 April to 29 May 2000. Map shows the location of the three general survey regions (northern, central, and southern). 2007 K.G. Chaulk and B. Turner 377 the highest altitudes, with elevation up to 350 m above sea level (asl) followed by the northern and central regions, with elevation as low as 2 m asl. The study area is typically described as sub-arctic, comprised of boreal forest, taiga, tundra, wetlands, lakes, river systems, and mountainous terrain. The frost-free period ranges from 40 days in the north to 100 days in the south (Department of National Defence 1994) Methods Survey methods Fourteen water systems were surveyed in helicopter over a 5-week period in the spring of 2000; these systems were grouped into three broad geographic sub-regions (north, central, and south). Each water system was visited once per week, and in total, 5 surveys were flown. Surveys were based out of Goose Bay, NL, and the weekly surveys were conducted from 27 April to 29 May, 2000. It should be noted that the labels north, central, and south are relative to this study, in that all survey sub-regions are located in Southern and Central Labrador, with the majority of sites located within Central Labrador. Surveys were conducted using an Enstrom EN-480 helicopter. Typical cruising speed was 110 km/h, but on-site survey speed ranged from 30–60 km/h, and on-site aboveground altitudes ranged from 15–30 m. Crew size varied from 2–3 people, but the pilot and primary researcher held constant for all surveys. Field observations, such as snow cover and species type and abundance, were collected using a laptop connected to a hand-held GPS unit and microphone. The GPS unit was mounted inside the aircraft with an unobstructed view of the sky. Geodetic coordinates were recorded in latitiude/longitude decimal degrees North American Datum 1983. The laptop was running the US Fish and Wildlife Service GPS Voice Survey Recording Program (v 3.1). The program was divided into 2 subprograms (record and transcribe). The record portion was used to collect field information and data-log flight-track information. By clicking the mouse pad, geodetic coordinates were linked to individual observations, stored in the form of audio files. The transcribe portion of the program was used to process the audio files and turn them into alpha numeric text (i.e., names and numbers). The post-processed data could then be exported to various software programs for mapping and data analysis. Post-processed data was saved as a database and stored in File Maker Pro (v 4.0), mapping was conducted in MapInfo (v 4.5), and statistical analyses and graphing were performed using Minitab (v 14.2). Sites were selected for observation based on a combination of previously identified spring staging habitats (Bateman et al. 1999), satellite imagery, and aboriginal environmental knowledge provided by Innu elders. In general, the water systems investigated in this study were those areas of first 378 Northeastern Naturalist Vol. 14, No. 3 open water in the spring and were selected due to their known or predicted importance to waterfowl spring staging, as they provide secure roosting sites and access to foraging habitat in an otherwise frozen landscape. Average snow cover was visually estimated for each site and compiled for each region. Waterfowl that were not positively identified were classed as one of the following: unidentified duck, unidentified diver, unidentified dabbler, or unidentified merganser/goldeneye, depending on the level of uncertainty of the observer. No effort was made to correct for potential auto-correlation of observations between survey weeks or regions. Sceintific names with authorities are given in Table 1 and species names are based on accounts from the Birds of North America. We used abundance and flock size to index the timing of waterfowl arrival and dispersion. Abundance and flock size are both expected to be highest in early spring periods when limited open water causes waterfowl to congregate. As many of these first open-water areas are not preferred breeding habitats, abundance and flock size are expected to decrease as spring progresses and waterfowl disperse to more favourable breeding and foraging habitats. Statistics We developed two separate general linear models with abundance as the response variable. Predictors in model 1 included: species, survey region, and their interaction. Predictors in model 2 included: species, survey week, Table 1. Summary of species and individuals for all regions all surveys. Observation made during weekly aerial surveys conducted in central Labrador from 27 April to 29 May, 2000. Total Total individuals # of flocks Average Scientific name Common name counted observed flock size Branta canadensis (L.) Canada Goose 6882 572 12.0 ± 1.2 Anas rupribes (Brewster) Black Duck 1252 356 3.5 ± 0.2 Anas crecca (L.) Green-winged Teal 934 117 8.0 ± 1.2 Bucephala clangula (L.) Common Goldeneye 906 270 3.4 ± 0.2 Aythya marila (L.) Greater Scaup 841 147 5.7 ± 0.8 Unknown duck 631 74 8.5 ± 1.7 Melanitta perspicilatta (L.) Surf Scoter 609 105 5.8 ± 0.7 Mergus spp. Unknown merganser 543 149 3.6 ± 0.5 Mergus merganser (L.) Common Merganser 211 61 3.5 ± 0.7 Anas acuta (L.) Northern Pintail 94 37 2.5 ± 0.3 Anas clypeata (L.) Northern Shoveler 71 18 3.9 ± 0.6 Anas platyrhynchos (L.) Mallard 57 24 2.4 ± 0.4 Unknown merg/gold 55 13 4.2 ± 0.5 Histronicus histronicus (L.) Harlequin Duck 45 16 2.8 ± 0.4 Aythya collaris (Donovan) Ringed-neck Duck 43 17 2.5 ± 0.3 Unknown diver 33 17 1.9 ± 0.2 Mergus serrator (L.) Red Breasted Merganser 22 11 2.0 ± 0.4 Melanitta nigra (L.) Black Scoter 21 6 3.5 ± 1.0 Melanitta fusca (L.) White Winged Scoter 7 2 3.5 ± 1.5 Anas Americana (Gmelin) American Wigeon 3 2 1.5 ± 0.5 2007 K.G. Chaulk and B. Turner 379 and their interaction. Unfortunately, due to rank deficiency resulting from limited sample size, we were precluded from using the model: species, survey week, survey region, and their interactions. Results Seasonal phenology Mean monthly temperatures for Goose Bay, the only reporting station within the study area, were above normal in April (observed = -0.3 oC; average = -1.8 oC) but below normal in May (observed = 4.3 oC ; average = 5.1 oC). Total precipitation was above normal in both April (observed 70.0 mm; average 57.1 mm) and May (observed = 101.0 mm; average = 66.4 mm). The study area was 99% snow-covered at the start of the survey period, decreasing to 0% for some sites by the end of the survey period. Spring melt did not occur uniformly, being faster at lower elevations in the central region and slower at higher elevations in the southern and northern regions. In all areas, at the time of the first survey (27 April), the ground was completely snow-covered, all lakes and streams were frozen, and open water was confined to only a few water systems in the southern region. Between 7 May and 15 May, the spring thaw was delayed by below-normal temperatures and above-normal precipitation, which fell as snow. Temperatures warmed during the third week, and extensive melting occurred by the last week of May (Fig. 2). Figure 2. Average percent snow-cover (95% CI), summarized by week and survey region. Snow-cover information based on repeated visual observations at 27 survey sites in the study area (one recording per site/per survey week). These 27 sites were pooled by survey sub-region (south, central, north). Observation made during weekly aerial surveys conducted in central Labrador from 27 April to 29 May, 2000. 380 Northeastern Naturalist Vol. 14, No. 3 Figure 3. Relative abundance by survey region for 6 species of waterfowl. Observations made during weekly aerial surveys conducted in Labrador from 27 April to 29 May, 2000. Note that the Y axes change by species. Overall diversity and abundance Over 13,000 individual waterfowl were counted between 27 April–29 May, 2000. In order, the five most abundant waterfowl were: Canada Goose, American Black Duck, Green-winged Teal, Common Goldeneye, and Greater Scaup (Table 1). Of observed waterfowl species, the 3 least abundant species were Black Scoter, White-winged Scoter, and American Wigeon, and overall, fifteen species of waterfowl were positively identified (Table 1). The northern region had the highest diversity (15 species), while the southern region had the lowest overall waterfowl diversity (11 species). The lowest waterfowl diversity was observed on the earliest survey date (27 April; 4 species), the greatest waterfowl diversity occurred on the latest survey date (29 May; 15 species). Spatial patterns We found that species and region had a significant interaction (P < 0.01, DF = 299, F = 1.88, R2 = 42.85%). Overall, the northern survey region had the highest counts for Canada Goose, Greater Scaup, and Common Goldeneye, the central survey region had the highest counts for Green-winged Teal and Black Duck, while Surf Scoters were equally abundant in the southern and northern regions (Fig. 3). Temporal patterns We found that species and week had a significant interaction (P < 0.01, DF = 299, F = 3.34, R2 = 62.15). Overall, Canada Goose abundance was 2007 K.G. Chaulk and B. Turner 381 highest on 7 May, while Green-winged Teal and Greater Scaup abundance peaked on 22 May. American Black Duck and Common Goldeneye abundance were greatest on 15 May, while Surf Scoters were late in arriving and were equally abundant on 22 and 29 May (Fig. 4). Average flock size varied by survey week depending on the species in question. Green-winged Teal flock sizes were relatively constant across survey dates (Fig. 5). Average flock size for Greater Scaup and Surf Scoter were lowest from 27 April to 7 May, and average flock sizes for Surf Scoter continued to increase as the survey period progressed, suggesting later nesting (Fig. 5). With respect to Canada Goose, American Black Duck, and Common Goldeneye, the largest average flock sizes were observed on 7 May, with flock sizes of these 3 species declining thereafter, most likely coinciding with the dispersal to breeding habitats (Fig. 5). The first active goose nests were observed in the central region on 29 May. Discussion With the exception of Canada Geese (Mowbray et al. 2002), the study area is near the range edge for many of the species observed including, American Black Duck, Green-winged Teal, Common Goldeneye, Surf Scoter, and Greater Scaup. The timing and extent of spring migration varies slightly for each species (Eadie et al. 1995, Johnson 1995, Kessel et al. 2002, Longcore et al. 2000, Savard et al. 1998). Unfortunately, very Figure 4. Relative abundance by survey week for 6 species of waterfowl. Observation made during weekly aerial surveys conducted in Labrador from 27 April to 29 May, 2000. Note that the Y axes change by species. 382 Northeastern Naturalist Vol. 14, No. 3 Figure 5. Average flock size summarized by week for 6 species of waterfowl. Observations made during weekly aerial surveys conducted in central Labrador from 27 April to 29 May, 2000. Dashed lines represent overall average flock size by species. Note that the Y axes change by species. The reader should note that the minimum error bar value for Green-winged Teal (date = 5/7) is negative and has not been truncated. few published reports exist with respect to the timing of spring migration in this sub-arctic region, so there is a paucity of information with respect to waterfowl staging during the spring period in Labrador. We found that the abundance of each species had a significant interaction with survey region, probably reflecting variable habitat conditions across regions. For example, latitude, elevation, vegetation, and wetlands could all play important roles influencing abundance patterns, with each species responding differently. Overall, the northern survey region was most productive for Canada Goose, Greater Scaup, and Common Goldeneye, while the central survey region was most productive for Green-winged Teal and American Black Duck; the southern and northern regions were equally productive for Surf Scoter. We also found that species abundance and survey week had a significant interaction; this was expected since each species has slightly different timing with respect to migration and consequently for the start of breeding and nesting. As the surveys were conducted during a single season, the findings should be considered more indicative than representative of temporal aspects of arrival and dispersal of waterfowl using spring staging habitats in Labrador. Additional surveys across several years are required to clearly establish annual variation. It should be noted that the timing of migration and subsequent nest initiation in more northerly areas of Labrador (>55o N) 2007 K.G. Chaulk and B. Turner 383 could be delayed by 1–3 weeks relative to our study areas, depending on the progress of spring. Unfortunately, we have limited information on which to make a generalized statement, but we do know that Somateria mollisima (L.)(Common Eiders) breeding in northern Labrador have average nestinitiation dates that can be 2–3 weeks later than Common Eiders nesting in more southern and central regions of Labrador (Chaulk et al. 2004). From late April to mid-May, we found that the amount of open-water habitat was quite limited, being restricted to fast-flowing rivers, river inlets and outlets, constrictions in lakes, and in the littoral areas of the tide-influenced central region. Snow cover appeared to vary with date, latitude, altitude, forest canopy cover, and presence of water (i.e., river, lake, wetland). Fast-moving rivers and drainage areas were the first to open, followed by lakes and wetlands; forested areas were the last to thaw. It should be noted that the study area was subjected to snow storms during the month of May, which resulted in increased snow cover for some areas as the spring progressed. The total numbers of observed waterfowl comprise but a small percentage of the total waterfowl estimated to breed in Labrador. Nonetheless, the results provide a basis on which to assess the timing and duration of spring migration for these six species. While total waterfowl numbers in each of the three regions (south, central, and north) followed a general pattern of increase to 7 May, and decreases after 22 May, species exhibited differences. For example, by 29 May, Surf Scoters were still increasing, while Canada Geese had largely dispersed from staging habitats. During Black Duck surveys in the 1990s (Bateman and Hicks 1999), Canada Goose goslings were observed as early as 29 May in the central survey region (K. Chaulk, pers. observ.), indicating nest initiation in late April. During our study, we did not observe any goslings, and the first active goose nest was not detected in the central region until 29 May 2000. However,with few exceptions (Chaulk et al. 2004, 2005), very little is published with respect to average nest-initiation dates for any waterfowl species in Labrador. Nonetheless, it appeared that the spring period in May 2000 was later arriving than normal, and it seems likely that goose nesting was delayed as a result. Of those species reported, Surf Scoter flock and overall abundance were still increasing at the end of the survey period, suggesting that this species has much later nesting than the other species, most likely starting in June (Savard and Lamothe 1991). Labrador is an important breeding area for many waterfowl populations of the Atlantic flyway, and our results may be of interest to regional researchers and managers. Our results could also serve as baseline information for studies investigating impacts of climate change on the timing of waterfowl migration, and might have application with respect to establishing spring hunting seasons for aboriginal people living in central Labrador. For example, the Labrador Inuit have finalized their land-claim process, which 384 Northeastern Naturalist Vol. 14, No. 3 provides waterfowl-harvesting rights during the spring period (LIA 2005). In the past, closing dates for the spring hunt have been based on traditional Inuit knowledge regarding the timing of transition from migration to nesting. The information presented here corresponds well with Inuit Knowledge, and may be useful in the co-management of the spring hunt in Nunatsiavut and surrounding areas. In addition, the information presented here may also be used to mitigate impacts of the Department of National Defence military flying program that operates out of Goose Bay, NL. 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