By GARY CHAMBERS
As you know, productivity conditions for these species at Karrak Lake south of Queen Maud Gulf (QMG) can be used to predict their age ratios in the fall when they move through Saskatchewan and on south. With that in mind, many folks have been asking “what was the hatch like?”.
Trouble is, because of evidence of phenological mismatch, some recent advancement of spring melt, high population densities, vegetation alteration, declining body condition of adults arriving to nest, and some unusually unfavorable weather during gosling growth, it has become difficult to predict what the age ratios during the fall flight are going to be, just from nest success. For example, you could have a really great hatch and still end up with virtually no goslings if weather conditions during gosling growth (between hatch and banding/fledging) are really bad for downy goslings (i.e., high winds, sustained heavy rains, and cooler temperatures). For that reason, we wait until banding in August to know what pre-fledging age ratios are from captures made by banders near Karrak Lake, since these correlate well with age ratios of live Snow and Ross’s geese in Saskatchewan during September and October.
Based on August age ratios, just reported to me by Kiel Drake of .07 goslings per adult Ross’s goose and .08 goslings per adult snow goose, the predicted age ratios in Saskatchewan are 0.04 and 0.08, respectively. I feel really confident that they will be less than 0.1 gosling per adult, or stated another way, there should be <10% young in light goose flocks that originate in QMG this fall.
We know that age ratios of both Snow and Ross’s geese, at both Karrak Lake and during fall migration through Saskatchewan, have been declining for the last almost 3 decades, but there has been virtually no production in 4 of the last 5 years (2015, 2016, 2018, 2019). As a result, the combined population of both species nesting at Karrak Lake has declined by over half in 6 years (from a high of almost 1.3 million in 2012, to 0.6 million in 2018…Dana Kellett and I don’t have the estimate yet for 2019, but it looks like another decline from 2018; I suspect that the entire midcontinent population might be in decline too).
There has been some emigration from Karrak Lake, but a lot of the recent nose-dive in numbers of breeding birds there appears to be the result of really poor recruitment, with no evidence of declining adult survival so far. Much of the variation in late summer/fall age ratios is related to gosling survival between hatch and banding, which has been in decline over the years as well.