The days are getting shorter and colder, and like some residents of Saskatchewan, many species of birds are making their way to warmer climates throughout North America.
While most migratory species have already returned to their winter homes, there are some that have decided to extend their stay in our province.
Dr. Mitch Weegman, Ducks Unlimited Canada Endowed Chair in Wetland and Waterfowl Conservation, joined us to shed some light on these hardy animals.
Now that the majority of bird migrations are completed, what can you tell us about the birds that choose to remain in the province?
The birds that are lingering now are a mixture of fairly hardy migrants and also some of the winter arrivals or residents. So, the winter arrivals are birds that are arriving from the north. They nest in the boreal forest or in the Arctic or subarctic.
These can be the small birds, like the bohemian waxwings but also quite large birds like the snowy owls that folks in Saskatchewan are perhaps used to seeing, and this is as far South as some of those species go.
Dr. Weegman explained that since artic and subarctic birds are well adjusted colder climes, with many spending much of the year between -20° and +10° range, making our portion of the province an attractive location to do their wintering.
While it makes sense that birds from the far north are staying here, it begs the question as to why some species are taking longer to journey south?
The lingering migrants which are going to be moving further south soon are taking advantage of (us having) no snow yet, and the relatively warm temps. Our wetlands and lakes are not frozen for the most part. So, these birds, waterfowl in particular that roost their sleep on the water, can still access those spots and the fields where these birds feed are still available.
Lots of grain waste from the harvest, these species are meeting their daily needs without taxing energy expenditure too much because they don't need to continue to keep warm as much as they would when we're under much colder conditions. These birds are staying until they they're pushed out basically by snow and ice.
Much akin to most other animals, the choice to stay in this location comes down to a simple matter of climate and convenience. But why do some species seem to go against their instincts and make the journey so much later?
It appears like migration like what we know today is migration is a mixture of day length and environmental conditions. So, the weather conditions that these birds experience. Even though lots of the waterfowl are well set up to still be in central Saskatchewan, southern Saskatchewan millions of ducks, geese, swans and cranes are now south of the province, even though the environment would allow them to be here.
I think the shortening of the day is really driving movement, not weather conditions. Snow and ice limiting literally how much they can feed or where they sleep, that kind of thing.
Do these different strategies have the potential to create new sub-species from the populations that choose to delay their migrations?
That is exactly what folks anticipate. There are multiple migration strategies among birds. There are long distance migrants which we typically regard as cross continental. Migrants that are going between North America and South America, there are short distance migrants, which we view as mostly migrating within the continent, so from, say, Saskatchewan to the central US or southern US. Then there are partial migrants, those partial migrants are species where some individuals of the species migrate, and others don’t.
Mallards are a pretty good example here, because they're so recognizable for folks in the province, we have mallards through a lot of the year because of these city parks and moving water areas where these birds can still make a living. Most mallards that nest here are headed to Arkansas and Oklahoma, and Kansas and Mississippi to winter.
Does this mean that we are already seeing the development of unique behavior that can lead to populations branching off into distinct groups?
(On an evolutionary timescale), we have quite a bit of evidence that it's likely that birds will continue to winter as far north as weather conditions allow and they may be then backing off on using day length as one of the primary drivers to move.
There are some more complicated elements like competition and also predation. In evolutionary time, a lot of the data suggests that these birds are moving because of competition. Even if they have the energy and the resources to stay in a particular place year-round the evolutionary pressures over many, many, many generations have been such that these birds are forced out.
They're losing competitive interactions, and so they're then forced to go further away, which is energetically expensive. They are heading to places where competition is less, or where predation pressures are less, they're avoiding these predation pressures by going somewhere else. So, it's not only on day length, temperature and ice and these things, there are other mechanisms at play.
Has the province’s transition from mostly prairie to farmland had a significant impact on the bird populations? Be it migrations, breeding locations or where food sources can be found?
The province is characterized today not by Short Grass Prairie and a mixture of wetlands as it would have been historically but, largely by agriculture. Agriculture is having some pretty influential impacts on a variety of our ecosystem’s species, including birds.
This is a huge feature of describing why regional populations may be declining or why across the prairies were most interested in some of the more sensitive grassland bird species because the grassland surrogate today is a collection of wheat and barley and canola, and it doesn't really serve the same purpose that it did evolutionarily for these species.
How has the study of these birds, their behavior, life cycles and migrations changed over the years?
We know so little about bird migration. People have been interested in bird migration for thousands of years, from Aristotle's writings to more recent developments. Over the last several hundred years people thought that Barnacle geese ( a species in Western Europe) actually wintered on the bottom of the ocean, so they have their name from barnacles, they also thought some birds migrated to the moon and back.
People have been fascinated by bird migration for a long time, and despite the level of interest, we still have lots of lingering questions about why they do it. And so now we have some pretty amazing technological and analytical tools to answer some of these big ecological questions.
What are some of the tools you are referring to?
We've been putting on thousands of tracking devices on these birds, variety of wetland dependent migratory birds, ducks, geese, shore, birds and smaller ones like tree swallows.
These devices collect location information, a GPS points every 15 minutes to an hour. They also collect a behavioral fix measured in three dimensions as well as an acceleration fix. The exact same sensor that's in our phone measures 3-dimensional movement every six to 10 minutes. Using that acceleration data, we can work out behavior. So, feeding, flying, sleeping. The normal activities that these birds undertake.
How long can these devices transmit data for?
The devices last a year or more, they often have a solar panel on them, so their batteries are rechargeable. They also upload their data daily via the global cellular phone network. So, we basically buy a cell phone plan for each bird, and we gain their data daily when they're in cell coverage areas.
We have thousands of devices on birds, so you can begin to learn the pressures on these species throughout the year, like basically where they most benefit, which habitats they gain the most energy in or which places they expend the most energy and which places contribute to how long they live, their annual survival rate, but also how many young they have during their reproductive season.
You can link all this and so you can begin to distill a migration that's thousands of kilometers into literally a couple quarter sections that in Saskatchewan say that differentially contribute to who lives, and who has their young.
In terms of conservation planning, there has been a revolution because now we can direct dollars to better a group of species in a way that's really targeted and then leverages money in the most efficient way possible. So this is really where we're headed with technology and analysis in conservation planning to help ensure that we have quite a nice biodiversity of bird species in Saskatchewan for many generations to come.
Where did your passion for nature, and in particular the study of birds come from?
I grew up in Minnesota in the northern US and I've always been interested in science. I've always been interested in understanding in a robust way how the natural world works.
I grew up hunting and fishing and spending a lot of time outdoors. Both of my parents were schoolteachers and so they took my twin brother, my sister and I all around camping and spending lots of time on the land.
In Grade 7 at my school, there was an opportunity to take an alternative science class where you were to develop a science fair project. Instead of learning normal biology and and genetics and so forth.
The whole point of the class was to ask a scientific question, basically, to follow the scientific method. Develop hypotheses, collect data, and then develop some inferences from your work to test your hypothesis.
I did that with waterfowl, with snow geese in in the late 90s and this developed over many years to competing regionally and nationally and internationally at these science fairs on waterfowl and on some of the pressures limiting population size of ducks.
I switched from snow geese to lesser scaup – one of our diving ducks in in the prairies – because they were declining rapidly in the late 90s and there were some leading hypotheses about why.
My twin brother Matt and I plugged into that, and that led to undergraduate research in the southern US, which is a wintering region for lots of our migratory birds, and understanding food availability in winter.
That led to graduate work in England. My wife and I moved there to study an Arctic nesting goose species – the Greenland White Fronted Goose – they breed in West Greenland; they stage in Iceland, and they winter in Ireland in Scotland.