Monthly Archives: May 2017

New details on nest preferences of declining sparrow

(Physorg 31 May 2017; Photo J. Winiarski)

Theory says that birds should choose nest sites that minimize their risk of predation, but studies often fail to show a connection between nest site selection and nest survival. Understanding these relationships can be key for managing declining species, and a new study from The Condor: Ornithological Applications explores the nest site preferences of Bachman’s Sparrow, a vulnerable songbird dependent on regularly burned longleaf pine forests in the southeastern U.S.

Jason Winiarski of North Carolina State University and his colleagues monitored a total of 132 Bachman’s Sparrow nests in two regions of North Carolina, the Coastal Plain and the Sandhills, measuring a variety of vegetation characteristics. They found several differences between the two regions in what sparrows looked for in a nest site—in the Coastal Plain, they favored low grass density and greater woody vegetation density, while birds in the Sandhills selected intermediate grass density and greater tree basal area. However, none of these features turned out to be related to nest survival.

According to the researchers, the differences between the two regions are likely due to differences in the available plant communities. Bachman’s Sparrows also could be selecting nest sites that allow easy access to nests or maximize the survival of fledglings once they leave, and these aspects may warrant further investigation. Regardless, Winiarski and his colleagues believe their results show the importance of management that mimics historical fire regimes in longleaf pine ecosystems, in order to maintain the diverse groundcover types used by the birds.

The most challenging part of the study was locating sparrow nests to monitor. “Bachman’s Sparrows are notoriously secretive and don’t easily give up the location of their well-hidden nests,” says Winiarski. “Eventually, we stumbled upon a technique of patiently watching adult sparrows at a distance that allowed the birds to behave normally, while being close enough for us to just barely see where they landed with food or nest material. That let us narrow down where the nest site was to within a few meters, and luck and thorough searching led us the rest of the way.”

“It is really remarkable that the authors were able to track the large number of Bachman’s Sparrow nests that they were able to find. As someone who has searched and searched for nests of this species, it is really hard,” according to Purdue University’s John Dunning, an expert on Bachman’s Sparrow ecology who was not involved with the research. “The study shows how consistent management of vegetation structure through the use of prescribed fire remains the most important management and conservation strategy to support breeding populations of Bachman’s Sparrow.”

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How capuchino seedeaters have such big differences in plumage despite little genetic diversity

(Bob Yirka 29 May 2017)
A team of researchers from the U.S., Brazil and Argentina has found clues that help explain why southern capuchino seedeaters have such wide differences in plumage despite being so closely genetically matched. In their paper published on the open access site Science Advances, the group describes the genetic analysis they conducted on the South American birds and what they found by doing so.

Southern capuchino seedeaters are a type of song bird, one of a group with familiar finch-like bills. They live in different parts of South America and have evolved in a unique way—the males have widely different plumage coloring and large differences in their songs. Prior research has shown that despite the differences in plumage, the birds are all quite genetically close. This led the team to wonder how or why that might be possible. They devised a theory that suggested that strong selection in an important part of the genome could perhaps lead to such differences. To find out if they were right, they conducted a DNA analysis of 56 individual birds from five species representing different plumages and found their genetic makeup to be nearly identical.

The team then took a closer look at the part of the genome known to be involved in creating melanins, a group of natural pigments. They found that 99 percent of the genome differences between the species occurred in such regions. But because speciation in seedeaters came about quickly, that led the researchers to suggest that it was due to actions by females—by exhibiting certain preferences in plumage or songs, the researchers theorize, the females were causing the males to adapt quickly.

The researchers conclude that natural selection due to female behavior has driven faster-than-normal speciation in the birds, resulting in wildly divergent plumage and song types—similar, they note, to the way the bills of Darwin’s finches have changed to adapt to conditions in the Galapagos. They suggest their work offers new insight into the ways strong genetic processes acting on a few key genes can bring about fast evolutionary changes.

Wind blows young migrant birds to all corners of Africa

(Universiteit van Amsterdam 24 May 2017)

Migrant birds that breed in the same area in Europe spread out across all of Africa during the northern winter. A new satellite-tracking study shows that the destination of individual birds is largely determined by the wind conditions they encounter during their first migration. The results were made available open access in the peer-reviewed journal Proceedings of the Royal Society B.

Until now little was known about how birds learn to migrate. Many young migrant birds die on their way to Africa, due to starvation, exhaustion or predation, or because they fall victim to hunters or collide with power lines and other human-made structures along the way. Wouter Vansteelant, lead author of the study, explains: ´As researchers we take a risk by tracking young birds with expensive tracking devices. Until now most people studied adult birds because they have a higher chance of survival. For this study, however, we decided to place satellite-tracking devices on 31 young honey buzzards that hatched from the egg in southwestern Finland.´

Of the 31 honey buzzards, 27 were able to start their first migration to Sub-Saharan Africa. Vansteelant: ´Twenty-four of these birds survived their first migration, ending up as far west as Mali and as far east as the Congo. The most western bird was located more than 3300km from the most eastern bird.´ The research team found that the location where the birds had ended up further west or east depended on the wind conditions they encountered along the way. ´We also saw that some individuals deviated from their average course to cross barriers. A quarter of the honey buzzards, for example, avoided the Baltic Sea by flying over land through Scandinavia, and therefore ended up further west than other birds, and further west than expected from the wind conditions they encountered alone´.

That young honey buzzards allow themselves to be drifted by the winds shows that their wintering destination is not predetermined genetically and that chance weather events decide where each individual will return to winter for the rest of its life. Vansteelant: ´We suspect this strategy is very common among migrant birds and probably developed at a time when plenty of suitable wintering habitats were available across the whole breadth of tropical Africa.´ It remains to be seen if that strategy will remain viable under ongoing habitat destruction due to intensification of agriculture, deforestation and climate change. ´If we want to conserve European breeding populations of migrant landbirds, we should focus on measures that will ensure preservation of suitable landscapes for these birds across many developing Sub-Saharan countries rather than the creation of a couple of scattered reserves.´


 

Sjælden fugl breder sig sydfra til hele Danmark

(Jan Skriver 24 May 2017)

For få årtier siden var rødtoppet fuglekonge en sjælden gæst i den danske natur. Men i disse år bliver fuglekongens fætter observeret over hele landet. Rødtoppet fuglekonge er vandret nordpå i takt med klimaændringerne, og Danmark er ved at blive et permanent yngleområde for denne sydlige art. Det viser Dansk Ornitologisk Forenings Atlas III, som er den hidtil mest omfattende undersøgelse af den danske fuglefauna.

Den vejer et sted mellem fem og ti gram, og dens stemme er så spinkel og musepibende højfrekvent, at mange mennesker har svært ved at høre den, selv om den synger alt, hvad den kan.

Men nu er det ganske vist, at rødtoppet fuglekonge, hvad angår geografisk udbredelse, er ved at sætte sig, så tungt som en fuglekonge nu engang formår, på de danske skovområder.

I hvert fald er antallet af observationer af denne traditionelt set sydlige og hidtil fåtallige fugleart i Danmark på det nærmeste eksploderet de senere år. Rødtoppet fuglekonge er tilsyneladende ved at blive en vidt udbredt dansk fugleart.

– Vi kan konstatere, at rødtoppet fuglekonge er i voldsom fremgang, og i disse år bliver arten set over hele landet. Vi kan se, at arten via Sønderjylland, Sydøstfyn og Sydsjælland år for år rykker længere og længere mod nord i Danmark. Og dén udvikling falder helt i tråd med forudsigelserne i det såkaldte klimaatlas, som den internationale fuglebeskyttelsesorganisation BirdLife International udgav for 10 år siden. Atlasset spåede blandt andet, at netop en art som rødtoppet fuglekonge ville ekspandere kraftigt mod lande i nord frem til omkring 2080, siger Thomas Vikstrøm, der er biolog i Dansk Ornitologisk Forening (DOF).

Han er med til at samle trådene i Atlas III, der er den hidtil mest omfattende kortlægning af Danmarks fuglefauna.

Tredobling i antallet af fund

Godt 1.400 medlemmer af Dansk Ornitologisk Forening (DOF) registrerer i fire år frem til foråret 2018 alle ynglefugle i landet, der er delt op i 2.262 kvadrater. Facit kan derpå sammenlignes med situationen i midten af 1990’erne, da Danmarks ynglefugle senest blev talt og estimeret.

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A little water goes a long way in helping birds during sizzling conditions

Swallows on telegraph wires

• Thermometers are set to sizzle this bank holiday weekend following on from the driest winter in more than 20 years
• Summer migrant birds returning from Africa such as swifts, swallows and house martins, as well as garden favourites like starlings, robins and blue tits could struggle to find a supply of water in hot conditions.
• Gardeners can help by following RSPB advice of leaving out a fresh supply of water to help birds through the breeding season.
With temperatures set to soar this bank holiday weekend and fears that the UK could face a widespread drought this summer, the RSPB is asking people to help birds through the hot conditions by making water available to them in their gardens or outdoor spaces.
Every year migrant birds such as swifts, swallows and house martins announce the arrival of the British summer as they complete a 6,000 mile migration from central and southern Africa to nest and raise their young. After the UK experienced its driest winter since 1995, these birds will arrive to conditions that will make building their nests from damp sticky mud much more difficult, which could impact on their chicks surviving.
The wildlife charity is appealing to people to put out a supply of fresh, clean water, as well as some wet mud in a shallow container like a dustbin lid, to help these migrant birds survive the arduous conditions.

Cowbird moms choosy when selecting foster parents for their young

(University of Illinois at Urbana-Champaign 23 May; Photo: Loren Merrill, Scott Chiavacci)

Brown-headed cowbirds are unconventional mothers. Rather than building nests and nurturing their chicks, they lay their eggs in the nests of other species, leaving their young ones to compete for resources with the foster parents’ own hatchlings. Despite their reputation as uncaring, absentee moms, cowbird mothers are capable of making sophisticated choices among potential nests in order to give their offspring a better chance of thriving, a new study shows.

Brown-headed cowbirds are known to lay their eggs in the nests of more than 200 other bird species of varying sizes, and typically do so after the host bird has laid her own eggs. The new study, led by a team at the University of Illinois, found that when cowbird mothers chose the nest of a larger host bird, they preferred those that held smaller-than-average eggs for that species. Smaller host eggs give the cowbird eggs a better chance of being successfully incubated; smaller host hatchlings mean the cowbird chicks face less competition for food and nest space.

“It implies a level of resolution in cowbird decision-making that people hadn’t seen before,” said Loren Merrill, a postdoctoral researcher at the Illinois Natural History Survey who conducted the study with INHS scientists Scott Chiavacci and Thomas Benson and Illinois State University researcher Ryan Paitz.

“Scientists originally saw cowbirds as egg dumpers that would put their eggs in any nest they found,” Merrill said. “And while that may be the case in some areas, or for some birds, it doesn’t tell the whole story. In fact, the more people have looked at cowbird behavior, the more our understanding has evolved of exactly how discriminating cowbirds can be.”

From April through August for five seasons ending in 2015, the researchers hunted through 16 shrubland sites across Illinois, looking for cowbirds and nests in which cowbirds might place their eggs.

“Nest searching is really fun fieldwork, except when you’re trekking through poison ivy- and hawthorn-infested lands,” Merrill said. “You either get really lucky and see nesting material in a bird’s mouth, and you watch until they lead you to a nest, or you listen and watch for the vocalizations and behaviors the adults use when you are close to a nest.”

Cowbirds use similar tactics to scout for host nests.

“They do a lot of skulking around the underbrush,” Merrill said. “They’ll also perch in an inconspicuous place and just watch. They are cuing in on the behavior of hosts that are building their nests or taking food back to nests.”

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”Biologisk mångfald – vår tids ödesfråga”

(SVT 22 maj 2017; Foto: Kerstin Joensson)

OPINION · ”Vikten av biologisk mångfald fastslås i forskningsrapport efter forskningsrapport, och vi vet att människor mår bättre av att leva nära en artrik natur. Det är hög tid att dessa slutsatser syns tydligare även i politiska och affärsmässiga beslut”, skriver företrädare för WWF, Naturskyddsföreningen, SOF BirdLife, Skydda skogen, Jordens Vänner, Fältbiologerna, Klimataktion Sverige, PUSH Sverige, Älväddarnas samorganisation och Urbergsgruppen Sverige.

I dag den 22 maj är det biologiska mångfaldens dag – en internationell högtidsdag, initierad av FN år 2002 för att öka förståelsen för en artrik natur.

Trots 15 års arbete med att lyfta frågan och trots att forskare anser att vi befinner oss i den sjätte stora massutrotningen av arter får sällan biologisk mångfald den uppmärksamhet som skulle behövas.

Klimatförändringarna och biologisk mångfald är vår tids stora ödesfrågor och det är två frågor som är sammanflätade. Artrik natur utgör hållbara system som lättare kan klara av klimatförändringar.

Bevarandet av naturskogar som lagrar stora mängder kol eller våtmarker som minskar övergödningen och gör samhället mindre sårbart mot översvämningar är bara två kända exempel i en lång rad av liknande exempel.

Samtidigt hotar klimatförändringarna artrikedomen när torrområden breder ut sig, korallrev bleks eller de arktiska istäcket blir allt mindre.

Den främsta anledningen till att den biologiska mångfalden minskar är också en av de största faktorerna bakom klimatförändringarna; vi släpper ut växthusgaser, vi hugger ner skogar och exploaterar naturen för att skapa jordbruksmark, monokulturer eller bebyggelse.

Samtidigt har kunskapen i ämnet aldrig varit så här stor.

Vikten av biologisk mångfald fastslås i forskningsrapport efter forskningsrapport, och vi vet att människor mår bättre av att leva nära en artrik natur.

Det är hög tid att dessa slutsatser syns tydligare även i politiska och affärsmässiga beslut.

Intresse för frågan saknas inte. I samband med den Biologiska mångfaldens dag den 22 maj arrangeras det cirka 60 aktiviteter runt om i landet.

Det invigs naturreservat, ordnas med fågelguidningar, skogsvandringar, naturbingo, naturpoesi i sociala medier och landsomfattande spindelräkningar. Skolor, naturföreningar, museum, naturum, länsstyrelser, turistföreningar och privata företag har engagerat sig för att visa vikten av den biologiska mångfalden.

Trots att kunskapen och intresset finns, tas frågan inte upp på allvar i den politiska debatten. Vi är framme vid ett vägskäl. De politiska besluten måste genomsyras av verklig hänsyn till naturen.

Vi kan inte längre anpassa oss efter de som vill fortsätta i samma hjulspår som om ingenting har hänt. Vi har i ett längre perspektiv inte råd med kortsiktighet.

Det är dags att även samhällets makthavare tar engagemanget och den samlade kunskapen på allvar och börjar agera för att rädda världens arter och livsmiljöer.

Att kunna bada i friska sjöar och vattendrag, att promenera i levande skogar, och att uppleva ett rikt växt- och djurliv som väcks av våren. Det är några av de livskvaliteter vi vill att kommande generationer också ska kunna njuta av, och som kan kräva tuffa politiska beslut.

Det att dags att inse att även det som kan tyckas vara oansenligt, faktiskt är ovärderligt.

Därför firar vi den biologiska mångfaldens dag och hoppas att frågan från och med nu får den uppmärksamhet som den förtjänar.