Birdsong Not Just For The Birds: Bio-acoustic Method Also Hears Nature’s Cry For Help

Switch on the mike, start the recording, the stage is set for the local fauna!

Computer scientists from the University of Bonn, in conjunction with the birdsong archives of Berlin’s Humboldt University, have developed a kind of ‘Big Brother’ for birds. This has nothing to do with entertainment, but a lot to do with the protection of nature. The new type of voice detector involved can reliably recognise the characteristic birdsong of different species of birds, thereby facilitating surveys of the bird population.

Europe’s forests are falling silent as countless species of birds go on the red list of endangered species. Yet in fact no-one can say what the exact position is with some species. So as to have a reliable count of the territories of indigenous birds it would practically be necessary to send out a whole horde of spare-time ornithologists to count the birds. What is more, since the birds are often hidden in the undergrowth or the tree tops, ornithologists need to rely on their ears and their specialist knowledge. This means that in many areas it is wellnigh impossible to map the bird population comprehensively and continuously.

Lees meer: Science Daily

Space use by Black-tailed Godwits Limosa limosa limosa during settlement at a previous or a new nest location

Auteur(s): Van Den Brink, V; Schroeder, J; Both, C; Lourenco, PM; Hooijmeijer, JCEW; Piersma, T
Bron: BIRD STUDY, 55: 188-193, Part 2; JUL 2008
Abstract: Black-tailed Godwits first return to the nest location of the previous year, even when moving to a different nest location later that season.

Aims: To examine the use of space by Black-tailed Godwits during the two months before egg-laying to two weeks afterwards.

Methods: We compare the spatial distribution of sightings of eventually site-faithful birds with birds that changed nest location, and relate this to the change of the distance to their previous year's and current nest-site in the period until egg-laying. Using a log-likelihood model we establish how the differences in distance to the respective nests change over the course of the season.

Results: All birds were observed first near their previous year's nest-site, and remained there for most of the pre-laying period. Birds that subsequently changed nest location made the move only about five days before egg-laying and were more wide-ranging earlier on.

Conclusion: The return to the previous nest-site suggests that a decision to move is made only after considerable time investment near the previous nest-site. This indicates that site-faithfulness in Black-tailed Godwits is conditional on experiences after return to the nesting area.

Bird evolutionary tree given a shake by DNA study

A new study – the largest analysis of birds to date using modern genetic methods – has turned up numerous surprising relationships that will force biologists to reevaluate much of what they thought they knew about avian evolution.

Until now, this evolutionary history has been something of a mystery, because most modern orders of birds arose in a sudden burst of innovation sometime between 65 and 100 million years ago. This left few intermediate forms to help biologists discern the evolutionary relationships among orders.

Lees meer: New Scientist

Acoustic information as a distant cue for habitat recognition by nocturnally migrating passerines during landfall

Auteur(s): Andrey Mukhin, Nikita Chernetsov, Dmitry Kishkinev
Bron: Behavioral Ecology 2008 19(4):716-723; doi:10.1093/beheco/arn025
Abstract: During migration, birds must fly over suboptimal habitats differing from those selected during breeding and wintering. Nocturnally migrating passerines need to assess the suitability of potential stopover habitats during landfall. Before actual landfall, distant cues may play a significant role in habitat selection.
In this paper, we studied the possibility that migrant songbirds use acoustic information as distant cues for habitat selection when ceasing flight. We also investigated differences between habitat generalists and specialists in their use of acoustic cues by comparing the proportion of species killed at lighthouses with those captured in mist nets using song playback in both suitable habitats and suboptimal stopover habitats during spring and fall migratory seasons.
Our observations showed that during twilight landfall, birds may respond to acoustic cues, especially when visual cues are reduced or absent. This was true for habitat specialists (Eurasian reed warblers and sedge warblers) whose songs are also more attractive to conspecifics and other birds of wetland habitats than to habitat generalists (pied flycatchers and redwings). Adult Eurasian reed warblers had a tendency to be more attracted by acoustic cues than juveniles. This finding suggests that previous experience may play a role in habitat recognition using acoustic stimuli.

Do birds have a good sense of smell?

Birds don't just see and hear well, their sense of smell is also highly developed.
The sense of smell might indeed be as important to birds as it is to fish or even mammals. This is the main conclusion of a study by Silke Steiger (Max Planck Institute for Ornithology) and her colleagues.

The sense of smell in birds was, until quite recently, thought to be poorly developed. Recent behavioural studies have shown that some bird species use their sense of smell to navigate, forage or even to distinguish individuals. Silke Steiger and her colleagues chose a genetic approach for their study. Their research focused on the olfactory receptor (OR) genes, which are expressed in sensory neurons within the olfactory epithelium, and constitute the molecular basis of the sense of smell. The total number of OR genes in a genome may reflect how many different scents an animal can detect or distinguish. In birds such genetic studies were previously restricted to the chicken, hitherto the only bird for which the full genomic sequence is known.

Lees meer: Eurekalert

Mortality of Black-tailed Godwit Limosa limosa and Northern Lapwing Vanellus vanellus chicks in wet grasslands: influence of predation and agriculture

Auteur(s): Hans Schekkerman, Wolf Teunissen, Ernst Oosterveld
Bron: JOURNAL OF ORNITHOLOGY DOI10.1007/s10336-008-0328-4
Abstract: Grassland-breeding shorebirds show widespread declines due to a reduction in breeding productivity following agricultural intensification. However, there is also concern that increasing predation causes further declines or precludes population recovery. Predation may itself be enhanced by agriculture through changes in habitat or food availability, but little is known about the mortality of nidifugous shorebird chicks. We studied mortality by radio-tagging 662 chicks of Black-tailed Godwit Limosa limosa and Northern Lapwing Vanellus vanellus in 15 farmland sites in the Netherlands. Tagging and handling had no effect on the condition and survival of godwit chicks, but body condition was reduced by 6–11% in lapwing chicks wearing a tag for longer than 3 days. Fledging success was 0–24% in both species.
Mortality was highest in young chicks but remained considerable until after fledging. Losses were traced mostly to predators (70–85%; 15 species, predominantly birds), but at least 5–10% were due to mowing, and 10–20% were due to other causes, including entrapment in ditches and starvation. Chicks staying in fields that were cut before the next radio check were found much more often as mowing victims and somewhat more often as prey remains than chicks in fields not cut, indicating that predation includes a limited amount of scavenging. The predation hazard for godwit chicks was higher in recently cut or grazed fields than in the tall, uncut grasslands they preferred, while that for lapwing chicks was lowest in grazed fields. In godwit chicks, poor body condition increased mortality risk, not only from starvation but also from other causes. Predation on godwit chicks was thus enhanced by intensive farming through a decline in the availability of cover, augmented by a reduced body condition, possibly due to food availability problems.
Changes in farming practice may therefore help reduce predation pressure, though the observed interactions explained only part of the high predation rate in godwits and none in lapwings. Predator abundance has increased in Dutch wet grassland regions, and chick predation has become a factor that should be considered in planning the type and location of conservation measures.

Reed warblers discriminate cuckoos from sparrowhawks with graded alarm signals that attract mates and neighbours

Auteur(s): J.A. Welbergen, N.B. Davies
Bron: ANIMAL BEHAVIOUR, doi:10.1016/j.anbehav.2008.03.020
Abstract: Brood parasites and predators pose unique threats that may favour the evolution of enemy-specific defence strategies. We considered whether reed warblers, Acrocephalus scirpaceus, have a specific alarm call for common cuckoos, Cuculus canorus, and whether their alarms attract mates and neighbours. Mounts of cuckoos (threat to nest but harmless to adults) were significantly more likely to be mobbed and were mobbed more strongly, with rasp calls and mandible snaps, than mounts of sparrowhawks, Accipiter nisus (threat to adults only), or teal, Anas crecca (a harmless control). However, calls were not acoustically specific to the kind of enemy presented, but rather varied in usage with mount distance from the nest and mount species.
This suggests that reed warbler alarm signals are not functionally referential, but rather convey immediacy of threat to the nest. Mates and neighbours often approached during calling, and playback experiments confirmed they were more likely to be attracted by mobbing calls than by control calls. The response was graded, with higher repetition rates of mobbing calls attracting more individuals. Nevertheless, it is unlikely that mobbing calls functioned solely to attract mates and neighbours because calling continued even after these were attracted and was not more likely when there were close neighbouring nests, and attracted neighbours were sometimes chased away by residents.
Our results show that reed warblers discriminate a brood parasite from both a dangerous species and an innocuous species by using graded alarm signals that attract conspecifics. This is compatible with the idea that nest defence by reed warblers includes a specific evolved response to brood parasitism.

Faux Hawk: Why Do Cuckoos Mimic Raptors?

Cuckoos are notorious freeloaders, conning other species into rearing their young, often at the expense of the hosts' chicks. But a new study suggests that the parasitic birds are not mere opportunists.

Like thieves who yell "fire" to clear a store before robbing it, cuckoos appear to have evolved hawklike plumage patterns and physical traits that temporarily scare potential hosts from their nests so they can lay eggs in them and get other birds to rear them.

Lees meer: Scientific American

Does ambient noise affect growth and begging call structure in nestling birds?

Auteur(s): Marty L. Leonard and Andrew G. Horn
Bron: Behavioral Ecology 2008 19(3):502-507; doi:10.1093/beheco/arm161
Abstract: Much of the research examining the effects of ambient noise on communication has focused on adult birds using acoustic signals in mate attraction and territory defense. Here, we examine the effects of noise exposure on young birds, which use acoustic signals to solicit food from parents.
We found that nestling tree swallows (Tachycineta bicolor) exposed to playbacks of white noise, within natural amplitude levels, from days 3 to 15 posthatch had begging calls with higher minimum frequencies and narrower frequency ranges than control nestlings raised in nests without added noise. Differences in begging call structure also persisted in the absence of noise. Two days after the noise was removed, experimental nestlings produced calls that were narrower in frequency range and less complex than control nestlings. We found no difference in growth between experimental and control nestlings.
Our results suggest that long-term noise exposure affects the structure of nestling begging calls. These effects persist in the absence of noise, suggesting that noise may affect how calls develop.

Vigilance benefits and competition costs in groups: do individual redshanks gain an overall foraging benefit?

Auteur(s): Sansom, A; Cresswell, W; Minderman, J; Lind, J
Bron: ANIMAL BEHAVIOUR, 75: 1869-1875, Part 6; JUN 2008
Abstract: Animals gain antipredation benefits from being in larger groups through increased probability of predator detection, dilution of individual risk of being attacked and confusion of predators during attack. A further benefit is that individuals in larger groups can decrease the amount of time they spend being vigilant, while maintaining a high probability of predator detection. They may then gain extra time to forage, so increasing overall intake rate.
Increasing group size, however, can also increase competition so that intake rates decrease.

We investigated whether there was a foraging benefit in redshanks, Tringa totanus, that show the group size decrease in individual vigilance. Intake rates did not change with group size, despite an increase in time spent foraging. Interference competition increased with group size because individuals travelled more to find prey. Redshanks used the extra time available to forage to maintain intake rates under increased competition.
Although the group size effect on vigilance did not accrue direct foraging benefits, larger groups formed, conferring other antipredation benefits. Intake rates were maintained because the interference competition was compensated by the benefits of reduced individual vigilance.
(c) 2008 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Who Dares Sings, And Who Sings Wins: Bold Birds Get The Girl

Humans often choose partners based on behavioural keys that are displayed during social interactions. The way we behave in different social contexts can reflect personality traits or temperament that may inspire long-term love. Behavioural norms that we perceive as sexually attractive are not culturally or evolutionarily arbitrary.

However, personality-mediated sexual selection is not just the privilege of mankind. In a new study László Garamszegiand colleagues at the University of Antwerp and at Eötvös University, Budapest used bird song as a model to investigate whether behavioural traits involved in sexual advertisement can serve as good indicators of personality in wild animals.

Lees meer: Science Daily

Full article: PLoS ONE

Superfast Muscles Power Songbird Singing

Some songbirds can contract their vocal muscles with the fastest muscle movements yet described — about 100 times faster than humans can blink an eye, according to new research.

The study found that two types of songbirds produce their tunes with superfast muscles, similar to those used by rattlesnakes, several fish and the ringdove (a type of pigeon).

Lees meer: Live Science

Birds Migrate Together At Night In Dispersed Flocks, New Study Indicates

A new analysis indicates that birds don’t fly alone when migrating at night. Some birds, at least, keep together on their migratory journeys, flying in tandem even when they are 200 meters or more apart.

The study, from researchers at the University of Illinois and the Illinois Natural History Survey, appears in Integrative and Comparative Biology in July. It is the first to confirm with statistical data what many ornithologists and observers had long suspected: Birds fly together in loose flocks during their nocturnal migration.

Lees meer: Science Daily

Migrating Songbirds Learn Survival Tips On The Fly

Migrating songbirds take their survival cues from local winged residents when flying through unfamiliar territory, a new Queen's University-led study shows.

It's a case of "When in Rome, do as the Romans do," says biologist Joseph Nocera, who conducted the research while working as an NSERC Postdoctoral Fellow at Queen's under the supervision of Biology professor Laurene Ratcliffe.

Avoiding predators can substantially increase a bird's chances of survival during migration, notes Dr. Nocera. But to do that, it first has to recognize who its predators are. "We believe some prey use social cues from other animals to gain information about potential predators," he says.

Lees meer:	Science Daily
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