In a Rocky Mountain Watershed I: BACKGROUND and GENERAL BREEDING ECOLOGY

Harlequin Duck breeding ecology 155 Harlequins H istrionicus histrionicus in a Rocky Mountain watershed I: BACKGROUND AND GENERAL BREEDING ECOLOGY Bill Hunt1 and Ron Ydenberg2* 'Banff Warden Office, Banff National Park Banff, Alberta, Canada TOL 0C0 2Behavioral Ecology Research Group, Department of Biological Sciences Simon Fraser University, Burnaby, British Columbia Canada V5A IS6. Telephone: + 1 604 291-4282, Fax: +1 604 291-3496; Email: [email protected] Corresponding Author The Maligne Valley, a watershed draining into the Athabasca River in the Rocky Mountains, in jasper National Park, Canada, is a breeding area for Harlequin Ducks (Histrionicus histrionicus). Based on peak counts, some 30 - 40 adults enter the valley each spring, arriving in early May along the Athabasca River. Numbers build steadily in the valley until the period of peak flow, and individuals are highly faithful to particular sections of the main watercourse. Feeding is intensive prior to nest initiation. Harlequins use lakes, outlets, rivers, and tributaries in the valley in a variety of ways. Along the Lower Maligne River, a few Harlequin pairs defend territories, but the majority of birds feed in aggregations at major lake outlets and inlets, likely highly productive places. On Maligne Lake birds feed in scattered pairs, generally situated at stream inlets. Females begin nesting in mid-}une following peak flow, and males depart the valley shortly thereafter. Nests are placed along both the main course of the Maligne River and along several tributaries, but the upper and lower sections of the Maligne River accounted for 11 of the 14 broods located. M any females move their broods to two large lakes for rearing. KeyWords: Harlequin Duck, Histrionicus histrionicus, Rocky Mountains, river outlets © Wildfowl & Wetlands Trust Wildfowl (2000) 51:155-168 156 Harlquin Duck breeding ecology Only a decade ago, Harlequin Ducks macroinvertebrate density (Bengtson & Histrionicus histrionicus were considered Ulfstrand 1971). In this paper a study of poorly known (Breault & Savard 1991), the breeding ecology of Harlequins in a but knowledge of their distribution, habitat Rocky Mountain valley is described. The requirements, and reproductive biology purpose is to establish their general have recently expanded (Robertson & phenology and ecology in this watershed, Goudie 1999).Their breeding ecology was as part of a larger study of how human first investigated in Iceland (Bengtson activities and climate change may be 1966; Bengtson 1972; Bengtson & affecting Harlequin ecology. Ulfstrand 1971). In western North America, many studies of breeding biology M ethods have been undertaken (Kuchel 1977; Dzinbal 1982; Dzinbal & Jarvis l982;Wallen 1987; Markum 1990; Cassirer & Groves Stud y A re a 1991; Schirato & Sharpe 1992; Wallen The study was conducted from May to 1992; Diamond & Finnegan 1993; Crowley September, 1993 to 1997, in the Maligne 1993; Zwiefelhofer 1994; Smith 2000) but Valley the watershed of a due to the low density of breeding (Figure I), second order stream that originates in the Harlequins most have been able to Rocky Mountains and descends over a observe only a few pairs. These studies distance of 70km to its confluence with indicate that Harlequins breed throughout the Athabasca River, near the town of the Western Cordillera, and are present Jasper, Alberta, Canada. The entire on mountain lakes and rivers from May to watershed is contained within Jasper September. As in Iceland, males actively National Park. defend their mates, while females focus on The main watercourse through the feeding (Inglis et al. 1991). Benthic Maligne Valley has six distinct sections. The macroinvertebrates, especially larval Upper Maligne River originates at an plecopterans, trichopterans and simuliids, altitude of about 2400m and flows into as well as other insects account for most Maligne Lake (altitude 1676m). W ater of the diet on breeding ranges, though fish leaves the lake almost silt-free at the eggs are taken opportunistically. Details Maligne Lake Outlet (M LO) and descends are known of plumages and moult through the Mid-Maligne River, entering (Robertson et al. 1997; Smith et al. 1998), Medicine Lake (altitude 1436m) through a pair formation (Gowans et al. 1997; braided gravel delta. Below Medicine Lake, Robertson et al. 1998), site fidelity the Lower Maligne River runs into the (Robertson et al. 1999), breeding Athabasca River at an elevation of I 100m. productivity (Crowley 1993), brood The Maligne watershed also contains I I rearing (Smith 2000) and recruitment tributaries judged potentially suitable for (Smith et al. submitted). Harlequin breeding (see Recent concern about sea duck F igu re I). Medicine Lake drains through a karst population trends (Goudie et al. 1994) has formation. In spring the flow of the Mid- prompted further study of the factors Maligne River into the lake rises and influencing sea duck populations. In Iceland exceeds the underground drainage rate; as at least, Harlequin productivity and habitat a consequence Medicine Lake fills in the selection seem linked to Harlequin Duck breeding ecology 157 Figure I. The Maligne Valley watershed in Jasper National Park, Alberta, Canada. Shading shows alpine areas, and the numbers identify tributaries given in Table 2. 158 Harlequin Duck breeding ecology course of the summer, but drains in winter Maligne Rivers. Stream flow diminishes when stream flow is reduced. The lake greatly in winter, though the Mid-Maligne does not drain directly into the course of River maintains a small, regular flow. Flow the Lower Maligne River except in rises abruptly in late May or June, and the occasional years of high freshet, when it ice leaves Maligne Lake over a period of may overflow. Instead, the Lower Maligne several days. W e termed this the ‘spring River is supplied with water by tributaries event’ and define it as the first day on and from a partial resurgence of the which the water level on the staff gauge at underground stream downstream of the M LO rose above 0.5m (see Figu re 2). Medicine Lake. From here, the Lower Maligne River descends gradually, until it Su rveys enters a narrow and steep canyon, below To monitor Harlequin abundance on the which it joins the Athabasca River. These Mid- and Lower Maligne Rivers, a weekly barriers prevent colonization, and the survey was conducted from the Maligne Lower Maligne River has few or no fish. Lake Road, which traverses the valley Environmental variables bottom from its confluence with the Athabasca to the MLO. Harlequins were Weather data were recorded daily at the counted from each of 37 viewing sites, Warden Station at Maligne Lake. Several which together give a nearly complete staff gauges and an automated stream flow view of the Lower Maligne River, Medicine recorder were used to monitor stream Lake, the Mid-Maligne River, and the MLO. flow at locations along the Mid- and Lower Banded individuals were identified DATE Figure 2. Typical examples of the seasonal course of water flow in the Maligne Valley, as measured on the staff guage at the Maligne Lake Outlet. The date of the‘spring event’ is defined as the first day on whch the water level rises above 0.5m. Harlequin Duck breeding ecology 159 whenever possible. Surveys began in the examined for signs of breeding, including first week of May, and after ice-out Maligne the development of a brood patch, pelvic Lake was surveyed on the same days, using opening, or the presence of an egg in the a small boat to patrol the lake perimeter at oviduct. The presence of a mate was also five to !0km/h, 10 to 50m from shore. noted. These surveys were concluded in late Food Sampling August. In addition to the weekly survey, the number of Harlequins at the Maligne In I 993-1995, the diversity and abundance Lake Outlet was counted every day. From of benthic macroinvertebrates was these data a peak count for each year was sampled at the M LO by collecting ‘kick’ derived, and the cumulative usage samples at two week intervals. This (measured in duck-weeks) of each section method was used because the substrates of the main watercourse was tabulated. at the M LO were too large to allow Unfortunately, the difficult access to the effective sampling with area samplers such Upper Maligne River meant that it could as the Hess or Serber samplers, and be surveyed only occasionally later in the Harlequins typically did not feed in shallow summer. areas or finer substrates. To collect a sample, one waded into the current and Tributary surveys kicked the substrate, within an From mid-June to early September of each approximate one square metre area, for year, hiking surveys were conducted along two minutes while holding a dip net (45cm the Maligne River tributaries shown on diameter), approximately 40cm Figu re I in search of Harlequin broods. downstream, to collect the invertebrates W hen possible the age of sighted broods as they washed off the substrate. was classified, based on body shape and Samples were preserved in 85% ethanol plumage development (Gollop & Marshall and sorted by hand under a dissecting 1954). Assuming 28 days incubation, a microscope, keying out invertebrates to mean clutch size of 5.7 and a typical laying family following Clifford (1980). Some interval of two days (Bengtson 1972), specimens could only be keyed only to hatch date (catch date minus estimated subclass or order (Annelida, Pelecypoda, age), the start of incubation (hatch date Hirundinea, and salmonid eggs). Each minus 28 days incubation) and the start of specimen (excluding salmonid eggs) was laying (start of incubation minus 12 days assigned to a foraging guild based on the laying) were estimated from the estimated primary foraging mode of the species age. within that taxa, after Cummins ( 1973), and into one of seven size classes, based Harlequin capture and banding on five millimetre increments.

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