KINGSTON, R.I. – April 17, 2024 – Migration and copy are two of essentially the most demanding occasions in a hen’s annual cycle, a lot in order that the overwhelming majority of migratory birds separate the 2 duties into totally different instances of the yr.
But a examine by University of Rhode Island researchers has discovered direct proof of a species – the American woodcock, a migratory shorebird from jap and central North America – that overlaps intervals of migration and copy, a uncommon breeding technique referred to as “itinerant breeding.” Their work, backed by collaborators throughout the East Coast, was revealed right this moment within the organic sciences journal Proceedings of the Royal Society B.
“I think this is a very exciting moment for bird researchers,” stated Colby Slezak, a URI Ph.D. scholar in organic and environmental sciences who led the examine. “It’s interesting to see that these distinct periods in a bird’s annual cycle are not so cut and dried. We often think of migration, breeding, fall migration and wintering as separate events. But woodcock are combining two of these into one period, which is interesting because both are so energetically expensive.”
“Each year the period of migration is distinct from the period of breeding in the vast majority of migratory birds, presumably because doing so at the same time is simply too costly,” stated Scott McWilliams, URI professor in pure assets science and principal investigator on the examine. “This paper provides the best documented case of a migratory bird that is an itinerant breeder. Such itinerant breeding is exceptionally rare, and documenting exceptions often proves the rules of nature.”
The American woodcock – additionally known as a timberdoodle, bogsucker, night time partridge, and Labrador tornado, amongst many extra – is a migratory shorebird that happens all through jap and central North America however its populations have been declining over the previous half century. The species is thought for its lengthy, needlelike invoice that may extract earthworms from deep within the floor and the males’ elaborate mating dance and “peent” name to draw females, Slezak stated.
While there are a few dozen hen species on the planet believed to be itinerant breeders, the examine is the primary to point out direct proof of the uncommon technique. “They’ve suspected other species of being itinerant breeders, but this is the first time we’ve had detailed GPS-tracking data and on-the-ground verification of nests to confirm that this was happening.” stated Slezak, of Broadalbin, New York.
To try this, the examine benefitted from the work of scores of biologists from federal, state and non-governmental companies alongside the American woodcock’s flyway, from the southern U.S. into Canada, who tagged greater than 350 females with GPS transmitters between 2019 and 2022. That initiative was a part of the University of Maine’s Eastern Woodcock Migration Research Cooperative.
Slezak, whose work on the examine was a part of his dissertation analysis, organized and analyzed the monitoring knowledge and alerted collaborators alongside the hen’s vary to confirm attainable nesting places. URI graduate college students Liam Corcoran, Megan Gray and Shannon Wesson additionally labored on different features of the woodcock venture, all a part of a collaborative analysis program with biologists from the Rhode Island Department of Environmental Management Division of Fish & Wildlife.
“I was looking for really short movement patterns during the breeding season to find suspected nests,” Slezak stated. “Relying on all of these collaborators from across the East Coast, I would reach out to them to tell them there was a suspected nest. They would travel out to the sites, sometimes quite far. It was amazing that we got the buy-in that we did.”
Based on GPS monitoring of greater than 200 females, the URI examine discovered that greater than 80% of the tagged females nested greater than as soon as throughout migration – some as much as six instances. During northward migration, females traveled a median of 800 kilometers between first and second nests, and shorter distances between subsequent nests, the examine stated. During 2021-22, URI researchers oversaw onsite verification of 26 nests from 22 females. Four females nested greater than as soon as, three of which migrated a considerable distance northward after their first nest try, the examine stated.
“There are many records of woodcock males singing along their migration routes, which has always been a mystery because it’s energetically expensive,” stated Slezak. “With this new data on females, we’re seeing that females are also nesting in the south early, moving north and nesting as they go. So, these males are probably getting breeding opportunities along the way.”
While migration and copy take quite a lot of vitality, American woodcock cut back the cost in different methods, Slezak stated. They have shorter migration distances than different species and have the pliability of utilizing numerous young-forest habitats. Also, females are bigger than males and their eggs are small relative to the scale of the females.
“A lot of birds probably can’t do it because they don’t have these lower reproductive costs that woodcock have evolved to do,” he stated.
Another evolutionary driver of itinerant breeding in woodcock may very well be predation. While they use quite a lot of habitats – wetlands, young forests with totally different tree sorts – they usually nest close to edges of open fields, leaving them vulnerable to quite a few predators.
“We think most of these post-nesting migratory movements are in response to predation events,” he stated. “They’re sitting on the nest and something comes and eats the eggs. The female takes off and keeps migrating north before trying to nest again. What we don’t know is: if the female has a successful nest, does she stop nesting the rest of the year?”
Despite regular declines in woodcock populations and their most popular young forest habitat over the past half century, the examine gives a glimmer of hope for woodcock, and different itinerant breeders going through the challenges of ongoing human growth and local weather change.
“Itinerant breeders may be more flexible in their response to environmental change because they are willing to breed in a wide variety of places,” stated Slezak. “So as long as some suitable habitat remains, the consequences may be less.”
