Tag Archives: tits

Great tits.

Different personalities help species face and adapt to threats, environmental changes

Personality may be adaptability’s trump card.

Great tits.

A pair of great tits (the bird).
Image via Pixabay.

Researchers at LMU Munich say that differences in personality could be a kind of insurance policy on the part of evolution. Different personalities, they report in a new paper, help maintain the level of biological variation needed to keep whole populations healthy and thriving.

Birds of a feather

The team focused their study on great tits (Parus major). The birds show some level of adaptability to environmental change, most notably through flexibility in choosing when to rear their chicks. High temperatures tend to make them build their nests and lay eggs earlier in the year, while colder temperatures make them put the whole matter off until the weather improves.

Natural selection favors such behavioral adaptability, the team explains, as long as the genetic variation is available — i.e. as long as the right genetic variants encoding reproductive behavior are present in the population, the birds will decide for themselves when is best to lay eggs, since that increases the chances their chicks will survive.

Personality is, at least in part, the source of this behavioral adaptability, the team reports. LMU behavioral biologist Niels Dingemanse and his doctoral student Robin Abbey-Lee have shown that the bolder among these birds lay their eggs earlier, when conditions allow it, while the shy ones wait for safe conditions, the team reports. In essence, their personalities allow them to interact with a threat (in this case, shifting weather) in different ways, which ensure that at least some members successfully rear their chicks.

The level of predation also has an influence on the timing and particularities of nesting behavior. The European sparrowhawk (Accipiter nisus) is a major predator of great tits, the team explains, with fledglings and young tits being the most vulnerable.

Sparrowhawks brood at a time when new generations of tits reach the fledgling stage, to make sure there will be plenty of pickings to feed baby sparrowhawks with. Some great tits, according to the team, react by deferring breeding, to give their offspring a higher chance of survival. They will also become markedly more alert and sing less often as they hear the call of a hunting sparrowhawk.

“In previous studies, however, we found that not all birds display this reaction to the same degree,” says Dingemanse. “Different individuals exhibit different personalities, and some are more explorative, daring and more aggressive than others.”

The team looked into whether these personality differences actually translate into a meaningful variation in the timing of breeding at the population level. During the breeding season – from April to June – the researchers exposed birds in a total of 12 tit populations to either the recorded call of the sparrowhawk or the song of the harmless blackbird.

Under these two conditions, the team explains, character differences did have an impact on the timing of breeding. More daring birds generally tend to explore their local environments more eagerly and thus breed later. The ones spooked by the team, however, began breeding earlier than what’s usual for great tits. Shier birds behaved exactly the opposite way.

It’s interesting to note that in the end, both personality types achieved essentially the same level of breeding success, according to the authors. This suggests that variation in personality does contribute to keeping a population’s genetic variability at healthy levels.

“In this way, populations can also become more resilient in the face of anthropogenic alterations of their environments, such as climate change,” Dingemanse points out.

The paper “Adaptive individual variation in phenological responses to perceived predation levels” has been published in the journal Nature Communications.

Great tits are evolving, new study shows

Birds helped early biologists develop the theory of evolution. Now, they’re showing us that evolution is still happening every day.

Great tits are evolving, and it might be because of us. Image credits: Fæ.

Setting up a bird feeder is one of the simplest ways to interact with wild birds. You probably either know exactly what I’m talking about or have no idea. That’s because bird feeders are very popular in some parts of the world, and almost unheard of in others. In the United Kingdom for instance, they’re a hit; and in the Netherlands, they’re not. Biologists wanted to see if this is having some effect on local birds, and they came up with some fascinating clues.

Great tits (Parus major) are some of the most common and most loved wild birds in Europe. As part of a long-term study, researchers from Netherlands and England screened DNA from more than 3,000 birds, looking for genetic differences between them — differences that might have been brought by natural selection.

“We know that evolution by natural selection produces peacocks’ tails and giraffes’ necks and that sort of thing,” says Spurgin, whose findings were published today in Science. “But it also works in much more subtle ways that are much more difficult to observe.”

Specifically, they were looking at genes which in humans affect face shape, and in great tits affect beak length. The driver of this change is believed to be the bird feeder, which allows birds with longer beaks to access more of the seeds. Indeed, researchers noticed a change in British tits, while Dutch tits remained unchanged. In only a few generations, evolutionary pressure started encouraging tits with longer beaks. Researchers also noticed that frequent visitors to bird feeders had longer beaks.

“Between the 1970s and the present day, beak length has got longer among the British birds. That’s a really short time period in which to see this sort of difference emerging,” says Professor Jon Slate, of the Department of Animal and Plant Sciences at the University of Sheffield.

“We now know that this increase in beak length, and the difference in beak length between birds in Britain and mainland Europe, is down to genes that have evolved by natural selection.”

Arkhat Abzhanov, a researcher in evolution and developmental genetics at Imperial College and Natural History Museum in London, called the study “a particularly good example” of combining genetic studies with the correlation of physical attributes.

To us, it’s a great reminder that evolution is still actively happening around us — and sometimes, we are the ones causing it.

Journal Reference: Mirte Bosse et al. Recent natural selection causes adaptive evolution of an avian polygenic trait. DOI: 10.1126/science.aal3298

Better looking specimens have healthier children, a study on great tits shows

Great tits are widespread species throughout Europe, the Middle East, Central and Northern Asia, and parts of North Africa in any sort of woodland. They tipically don’t migrate, except for very harsh winters. According to a new paper published in BioMed Central’s open access journal Frontiers in Zoology, the female’s appearance can be correlated with healthy attributes in offspring.

tits

The black stripe across her breast and white patches on her cheeks correlate to a chick’s weight at two weeks and immune strength respectively – thought the former can be in fact a genetic trait, while the latter can be an effect of nurture rather than nature.

However, researchers from Palacky University in the Czech Republic played a nasty trick on a pair of tits, swapping their offspring to test their theories. They investigated the growth and health of the infants and the ‘ornamentation’ of their mothers. The factors they took into consideration were weight, size and immune strength. What they found was that indeed, there is a correlation between the chick’s weight at two weeks and the size of black breast stripe on the genetic mother.

The body size of the chick is only related to its mother’s body size, and not its ornamentation, but strength of chick’s immune response was in fact connected to the white cheek patch. Talking about how the ornaments evolved to represent other bodily traits, Vladimír Remeš and Beata Matysioková who performed this study explained:

“Bigger healthier babies are important to the reproductive success of individuals, because they are more likely to survive to adulthood — so it is useful for birds to be able to work out which potential mates will produce the best babies. Maintaining bright colouration uses up resources which could otherwise be invested in reproduction or self-maintenance — consequently the evolution and maintenance of ornamentation in female great tits is probably due to direct selection by males.”