The Birds of Whitewater Lake

photos and article by: Tim Poole

The summer of 2017 has been a long, exhausting, but successful rollercoaster for the Manitoba Important Bird Areas (IBA) Program -  with more events, more trips and even more birds. Our volunteers have visited and monitored over half of Manitoba’s (now) 35 IBAs - from the northern shores of Hudson Bay, to the far southwest corner via the Saskatchewan River Delta around The Pas, and the Interlake. Whether as part of an organised IBA blitz, a Nature Manitoba birding outing, or an individual birding trip, our volunteers have managed to locate impressive numbers of birds across our IBA network this year - including a phenomenal 9,216 Tundra Swans counted in the Saskatchewan River Delta IBA, 723 Western Grebe at Sandy Bay Marshes IBA and 1,605 American White Pelicans at North, West and East Shoal Lakes IBA.

For those familiar with birding in Manitoba, it will be no surprise that Whitewater Lake has again returned some of the most impressive figures for Manitoba in 2017.

Whitewater Lake, a south-western Manitoba IBA, is probably our premier birding location for shorebirds and long-legged waders. Its unique physical features make Whitewater a significant lake for birds and biodiversity. Nestled in the shadow of Turtle Mountain, this is both a terminal basin (a lake with an inflow but no outflow) and alkaline lake. Water levels will fluctuate greatly over decades, at some points drying to a dustbowl, and at sometimes full to overflowing. Being a terminal basin, the lack of outflow can cause significant changes in the wider environment. The nature of this lake and the lack of an outflow has been the subject of much discussion over the past few years.

Large fluctuations in water levels are part of the natural cycle for these prairies wetlands. Low water levels create the ideal conditions for emergent vegetation. This vegetation is the source of food and habitat for so many of the species which depend on these wetlands. Alkaline lakes also often contain large concentrations of brine shrimps and other invertebrates, a favoured food for shorebirds.

Colin Blyth and Gillian Richards, our brilliant IBA caretakers for Whitewater Lake, make regular trips to the lake throughout the year to monitor bird populations and habitats. They are also strong advocates for the IBA Program in an area where locals have mixed feelings about the lake, due to the current flooding of agricultural land in wetter years.

This year, Colin and Gillian confirmed Manitoba’s only known successful breeding attempt of the Piping Plover for 2017 at Whitewater. Among many other highlights, they also found Cinnamon Teal (a rarity in Manitoba), and were also present to count about twenty thousand Snow Geese in spring and fall.

On May 21st, we had our first Whitewater IBA bird blitz for 2017. Among the highlights were over 1,000 Western Grebes, a species of Special Concern which was recently added to the Species At Risk Act.

Another colonial waterbird which nests at Whitewater Lake in incredible numbers is the Franklin’s Gull. It can be difficult to find the colonies currently with access to the lake shore tricky in many places, but in 2007, when the estimated size of the colony was around 180,000 gulls, the birds could be observed from the now defunct dyke system. There were also over 20 species of shorebird, including very good numbers of Black-bellied Plover, as well as two different Glossy Ibis, a rare breeding species in Manitoba.

We returned to Whitewater for two late summer blitzes in August. The first of these was on August 6^th and the second on August 27^th. Our primary objective was to seek out large concentrations of migratory shorebirds. In total we counted a minimum of 12,525 shorebirds representing 25 different species between the two dates. Of particular importance were the large numbers of dowitchers.

The Short-billed Dowitcher peak was from August 6^th (4,810) and Long-billed Dowitcher peak from August 27^th (2,196). Both these figures are greater than the 1% estimated global populations for these species, which means that Whitewater Lake is a globally significant site for both dowitchers. Identifying dowitchers to species level can be difficult in fall, and we have tried to explain more about how to do this on our blog.

Large pre-migratory flocks of American Avocet also congregate at Whitewater Lake - 1,938 on the 27^th being the peak this year. In some years the peak exceeds 3,000 avocets swirling in large flocks in the shallow waters along the lake edge. 997 Stilt Sandpipers was another impressive total from August 6th. Three Buff-breasted Sandpiper, a threatened species which breeds in the High Arctic and winters in the grasslands of South America, were noted, although the sod farms on the northern boundary of Oak Hammock Marsh were the best place to find them in 2017. You can see the summary of the highest totals for both blitzes at Whitewater Lake in the table below.

At least 20,472 waterfowl were counted on August 27^th – but it was still early in waterfowl migration season. The most numerous species over both dates was the Mallard, with over 6,700 counted on August 6^th. Similar numbers of American Coot were counted on the same day. Pelicans and cormorants also gathered in impressive numbers, and there was an impressive colony of Eared Grebe here, with 2,075 being counted on August 6^th.

The numbers of Western Grebe here are phenomenal, and the totals encountered on both blitzes were impressive. It is our view that Whitewater Lake must currently have one of the most important breeding colonies of this species anywhere in Canada. 4,098 were counted on August 6^th, over 3% of the species global population. Please note though that there are other important sites in Manitoba for this species including Delta Marsh, Marshy Point and Sandy Bay Marshes, all IBAs. The highest total count for some of these waterbirds are outlined below.

Whitewater has long been considered as the best place in Manitoba to find long-legged wading birds. The most numerous species across these blitzes was our most recent colonist, the White-faced Ibis. Since establishing itself in Manitoba at Whitewater in the mid-2000’s, its range has expanded in the southwest to include Oak Lake and Plum Lakes IBA and the Maple Lakes. Cattle Egret are a regular presence in pastures both north and south of the lake, where they wait patiently for cattle to disturb potential prey in the grass, pouncing on the unsuspecting critter as it makes its escape.

Whitewater is also the best place in Manitoba for the Snowy Egret. The distinct yellow foot of this elegant heron is apparently used as a lure for fish. As you can see from the table below, Great Egret and Black-crowned Night Heron are also present in good numbers.

Gulls and terns breed here in good numbers. The aforementioned Franklin’s Gulls is the most numerous species. There are also large numbers of breeding Forster’s Terns and Black Terns here. The occasional California Gull is always worth looking out for in flocks of Ring-billed Gull and one did turn up this fall.

Swallows gathered in phenomenal numbers. The Species At Risk Act was recently amended to include the Bank Swallow - a species seemingly so numerous yet suffering long-term declines across Canada. It was therefore very promising that we counted nearly 24,000 on the 6^th in large pre-migratory flocks. There were swallows literally everywhere: on roads, powerlines, and drinking in pools. A truly impressive sight! Tree Swallow numbers were also high on both dates.

These are just some highlights from two very successful days out at Whitewater Lake. In total across two blitzes, we counted 84,630 individual birds representing 118 different species. The highlights were certainly the globally significant concentrations of Western Grebe, Short-billed Dowitcher and Long-billed Dowitcher.

Finally, thank you to our supporters and volunteers for your contributions in 2017. We are especially grateful to Environment Canada’s EcoaAction Community Funding Program, TD Friends of the Environment Foundation, the Blennerhassett Family Foundation, Assiniboine Credit Union, the McClean Foundation, Nature Canada and Manitoba Community Service Council for their financial support.

If you would like to hear more about the Manitoba IBA Program or are interested in volunteering in future events, please email Tim Poole at iba@naturemanitoba.ca.