Tag Archives: breeding

Wind, rain play key role in breeding patterns of migratory tree swallows

https://upload.wikimedia.org/wikipedia/commons/d/dc/7Z1E7819.jpg(Physorg, University of Colorado; Photo Wikipedia; 25 April 2017)

Wind and precipitation play a crucial role in advancing or delaying the breeding cycles of North American tree swallows, according to the results of a new University of Colorado Boulder-led study.

The research, which appears today in the journal Proceedings of the Royal Society B, sheds new light on how wet, windy weather can affect tree swallow nesting and underscores the importance of considering factors beyond temperature when examining how climate change might affect species’ biological niche.

Over the past decade and a half, the average egg hatching date for tree swallows—a common migratory bird species that winters in temperate southern climates before nesting in the spring at sites across North America, including the sub-Arctic regions covered in the study—has shifted earlier in the year by an average of six days. This change is similar to, but considerably greater than, changes seen in more southerly sites and until now has been believed to correlate with rising temperatures.

However, when CU Boulder researchers tested how swallow nesting data from two different Alaskan sites corresponded with both daily and seasonal climate indicators like the number of windy days, days with measureable precipitation and average daily temperature, they found that windiness (or lack thereof) had the most consistent correlation with swallow breeding patterns over time.

“We expected that temperature and precipitation would be much more strongly predictive than wind,” said Daniel Doak, a professor in CU Boulder’s Environmental Studies Program and the co-author of the new research. “The study demonstrates that fine-scale climate effects are important to consider when thinking about what’s going to affect a species.”

The study developed as a result of a CU Boulder undergraduate’s research efforts. Rachel Irons, then a junior in the Department of Ecology and Evolutionary Biology, received a UROP grant and worked with the Alaska Department of Fish and Game on a long-term tree swallow nesting study to fulfill her senior thesis requirements.

“Swallow phenology in Alaska is shifting at twice the rate of the continental U.S.,” said Irons, who is the lead author of the new paper. “I figured it was related to temperature, but I added in wind and precipitation measurements just to get the whole climate picture.”

The results showed that a long-term decline in windiness (and to a more variable extent, rain) in central Alaska over the past decade-plus correlated with the birds’ earlier breeding much more strongly than temperature, indicating that wet, windy spring weather that may have delayed egg laying in the past is now less of an impediment for the swallows.

The authors noted that while it is not necessarily surprising that wind and rain would affect an aerial foraging species like tree swallows, the findings emphasize the need to broaden the scope of consideration when making predictions about which climate mechanisms will influence population ecology.

“This shows that our initial intuitions are not always good about what’s going to impact these birds and their patterns,” said Doak.

Western Australia’s inland lakes become breeding grounds for thousands of waterbirds

Thousands of bird fly over an island in the western desert

(Eliza Wood; 31 Mar 2017)

Western Australia’s northern desert region has been transformed into a breeding ground for thousands of waterbirds following a record-breaking wet season.

In the area from the East Pilbara to the Northern Territory border, the salt pans have filled to the highest level in 30 years.

Staff from the Indigenous Desert Alliance and Parks and Wildlife surveyed the area recently by plane.

Alliance spokesman Gareth Catt said the usually-coastal birds would have flown in from as far as South Australia as soon as heavy rains began.

“January had more than double the record rain at Telfer [in the East Pilbara], so we knew that it was very likely that some of the lakes had filled,” Mr Catt said.

“So we went out to see what birds might be on those lakes and found some colonies of tens of thousands of birds in some locations.”

On one lake Mr Catt estimated there were 90,000 banded stilts.

“It was absolutely spectacular, and beyond our expectations of what we might find,” he said.

“Not a whole lot is known about the banded stilt.

“We know that they spend a lot of their time on the coast, and they come inland immediately as rain starts to fall with these big events.

“They’re a colonial breeder; they seem to be really on top of each other [and] were on the smallest islands in the middle of the lakes in [the] tens of thousands.”

Chicks and eggs in nests spotted

Mr Catt said the filling of the lakes and the arrival of the birds for breeding was ecologically significant.

“We’re expecting that there would be enough water from this fill event for the birds to breed at least once and to be successful,” he said.

“In some locations we saw chicks that had just recently hatched but in most places, the birds were sitting on eggs when we were looking at the nesting sites.”

He said while the desert had not had rain like this for 30 years, the likelihood of it happening again soon was increasing.

“With climate change, the north-western desert is starting to get more frequent rain events over summer,” Mr Catt said.

“So the interval between these big rain events is getting shorter [and] it could be that the desert becomes a bit more green in the future.”

Stressed seabird parents think only of themselves

(Dorota Kidawa 10 March 2017)
Stress is a factor not only in the best human families; it also appears among animals. To see how bird family members interact with each other in stressful situations, researchers from Vetmeduni Vienna and the University of Gdansk, Poland, studied parent-offspring interactions in a long-lived seabird, the little auk (Alle alle). The scientists gave parent and offspring birds a hormone pellet to increase their “stress levels”, with the result that stressed offspring not only intensified their begging but also received more food than “relaxed” chicks. Nevertheless, increased begging was not the determining factor of the parent-offspring interaction. When parent birds were stressed, they automatically reduced offspring feeding and spent more time searching for food for themselves. The parent-offspring interaction among little auks therefore clearly depended on the state of the adult bird, even though little auks usually raise only a single chick. The results have been published in the Journal of Ornithology.

ittle auks (Alle alle) breed in large colonies on rocky cliffsides in arctic regions. These seabirds live in a harsh environment and often face stress in the form of food shortages and poor weather conditions. But this isn’t the only thing that makes them so suitable to study stress-induced behavioural mechanisms. They also are of interest for their long lifespan and because little auks raise only a single chick during the year, which excludes sibling rivalry as a factor in stress studies. A team of researchers from Vetmeduni Vienna and the University of Gdansk in Poland thus attained informative insights into the interaction between long-lived birds and their offspring.

Stress behaviour in birds controlled by hormones

“Birds respond to stressful situations by releasing the hormone corticosterone,” explains senior author Rupert Palme from the Department of Physiology, Pathophysiology and Experimental Endocrinology at Vetmeduni Vienna. This makes corticosterone an important stress indicator in behavioural studies. Hormone pellets can be used to artificially release corticosterone into the birds’ bloodstream in order to observe the animals’ behaviour under stress. The pellets have the advantage that corticosterone is released in a controlled fashion continuously over a certain period of time. An analysis of faecal samples can be used to show that the additional hormone was metabolised by the body. The internationally recognised method of measuring faecal hormone metabolites was developed by senior author Palme.

To analyse the mechanisms controlling familiar interactions among little auks, the researchers first implanted offspring birds, then parents with hormone-releasing pellets. Chick behaviour was analysed using acoustic recordings, that of the parents by looking at feeding intervals and time spent away from the nest or colony.

Little auk offspring come in second place

Nestlings responded to the artificially heightened stress levels by increasing their begging performance. “More food means more reserves, better fitness and, therefore, a higher chance of survival,” says first author Dorota Kidawa from the University of Gdansk, Poland. “The intensified begging behaviour was a cry for help directed at the parent birds that was clearly successful.” The stressed offspring weighed more than the control chicks, which indicates that they had been fed more frequently by the parent birds. “Our study shows that adult little auks usually go to their limit, to their caring maximum, in order to give their offspring enough to eat,” says Palme.

The second test, however, in which the researchers implanted a hormone pellet into one of the parent birds, showed that this limit depends on the stress level of the parent bird and not on the begging behaviour of the young little auks. Under stress, parent birds alter their behaviour to their own benefit. They left the nest for longer periods of time to provide more food for themselves. As a result, they fed their young less frequently and the physical state of the offspring worsened considerably compared to the control group.

Despite egoistic survival instinct, the birds are not bad parents

“The begging behaviour elicited a care response among the adult little auks. But this response, and its extent, depend on how fit the parent birds feel,” says Palme. If their own chance of survival is reduced because of a food shortage or weather conditions, they will focus more on themselves and spend more time looking for their own food than on the care of their only chick.

“But that doesn’t make them bad parents,” says Palme. “This is a normal occurrence in nature that cannot be compared to our behaviour and sense of responsibility.” For the long-lived little auks, it is more important to secure their own existence, to survive another year and to raise another offspring in the future. After all, poor food conditions and environmental factors can also reduce the young birds’ chance of survival.

How Will an Arctic-Breeding Songbird Respond to Taller Shrubs and Warmer Temperatures?

(Heather McFarland, 1 Feb, 2017)

How will songbirds that nest in tundra respond as the Arctic transforms into a warmer and shrubbier environment? This is the question that drove us to study a small songbird known as the Smith’s Longspur. Endemic to North America, this songbird breeds in only a few remote mountain valleys in Canada and Alaska, making it particularly susceptible to changes at northern latitudes. Smith’s Longspur’s are also unique in that they are polygynandrous. This is a rare mating strategy where both sexes are polygamous, and birds of either sex may mate with up to three individuals each breeding season. Rather than a single male and female establishing a territory, Smith’s Longspurs usually form larger groups called neighborhoods which contain many inter-mated individuals. Since this mating strategy is poorly understood and so different from other tundra nesting songbirds, it is difficult to predict how breeding Smith’s Longspurs may respond to climate change. Therefore, prior to further change, baseline information about breeding requirements is needed. To fill this void, we monitored more than 250 Smith’s Longspur nests between 2007 and 2013 in the Brooks Range of Alaska. All of the nests were found in open tundra areas, and females never placed their nests in tall vegetation.

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