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Ornithology: Project Sapsucker Results

Beginning in 1998, seven volunteers, the Project coordinator and a Quebec/Alberta exchange student located and scored parent sapsuckers at over 35 nests in the Eastern Slopes region of the Rocky Mountains of Alberta, spanning an area from near Sundre in the north to Kananaskis Country and Okotoks in the south, mostly on public land, but also on private land (Figure 1). Volunteers also looked for sapsuckers as far afield as Pincher Creek, Dinosaur Provincial Park, and around Nordegg. The goal of the project is to document parent sapsuckers at more than 100 nests, so more work remains to be done.

To date, our data confirm extensive hybridization between the two species of sapsuckers in western Alberta. Forty-one percent of parent sapsuckers in the hybrid zone (from about the James River west of Sundre to the Sheep River in Kananaskis Country) in 1998 and 1999 displayed mixed or intermediate characteristics (scores of 2 to 6: hybrids), while 25 % of nests had parents of markedly different appearance (differing by more than 3 points on the hybrid scale: mixed pairs).

In previous years hybrids or mixed pairs also were observed along the Clearwater River west of Caroline and along Beaver Creek in the Porcupine Hills. Specimens in collections at the Royal Alberta Museum and the University of Alberta with intermediate characteristics (scores of 2 to 6) come from as far as the Swan Hills, Lac La Biche, Battle River south of Hardisty, and, in the south, Lynx Creek (Figure 1).

The degree and geographical extent of hybridization between the two Alberta species and apparent lack of reproductive barriers between them suggest that their current separate specific status should probably be reconsidered. It would probably be more appropriate to lump the two forms together under one species, as has been done with the Northern Flicker, Yellow-rumped Warbler and Dark-eyed Junco.

Figure 3 Figure 2 Probably the greatest surprise to come out of Project Sapsucker has been a demonstration of just how dynamic the situation in the Eastern Slopes is. In the three years since the Royal Alberta Museum began compiling information on sapsuckers of the Eastern Slopes in 1996, there have been dramatic changes in the make-up of populations of sapsuckers. For example, in 1996 54% of birds in Kananaskis Country consisted of relatively pure types (scores 0-1 or 7-8), while in 1998 86% of sapsuckers scored as hybrids (scores 2 to 6) (Figure 2). Further, in 1996 and 1997 there were many mixed pairs or hybrids along the Clearwater River west of Caroline, at the northern limit of the hybrid zone, but in 1998 there were none (Figure 3). This suggests that the hybrid zone is very dynamic. The hybrid zone might be broadening or shifting geographically with time, perhaps as a result of human activity in the Eastern Slopes or further north or south. But this needs not be the case. The make-up of sapsucker populations in the hybrid zone is a function of both local production of young (mostly hybrids) and immigration of pure types from the north (Yellow-bellied) and the south (Red-naped). It is conceivable that in some years northern birds are more successful at raising young (presumably because of favorable climatic conditions in the boreal forest) than southern birds, and will contribute proportionately more birds to the hybrid zone in subsequent years. As a result the hybrid zone could shift southward. In other years the reverse could be true. This situation could be likened to a genetic tug-of-war of sorts between two forms of relatively equal "strength".

So how can we distinguish between these two very different scenarios? With historical data. Unfortunately there is next to no information available on the sapsucker situation in Alberta in the recent past. This explains, in part, why the decision to split the two species was never based on information from Alberta. This may be about to change if the current effort can be sustained!

The year 2000 should be an interesting one: 1999 was a disastrous year for sapsuckers (and other birds) in the Eastern Slopes of Alberta due to the rather inclement weather that summer. Only one of nine nest sites visited in 1999 along the James River west of Sundre was active in early July. Several nests, as indicated by fresh holes, were abandoned that summer. Only one other active nest was found along the James River in 1999. It is probable that as a result of the poor production of hybrids in 1999, pure types will be well represented in Eastern Slopes forests in 2000. At least that is a prediction that will be tested in 2000.

So Project Sapsucker still needs volunteers to help answer some of the questions raised in 1998 and 1999. The experience promises to be exciting. In the words of one participant "Thank you for being part of this study".

Interesting observations made in 1998 and 1999: