Category Archives: Birds

Young African penguins are dying because they can’t find the fish they need

Katrin Ludynia, University of Cape Town and Richard Sherley, University of Exeter

When young African penguins leave their nests for the first time they do so alone, without any guidance from their parents. They need to use their instinct to follow cues in their environment to find food and stay alive in their first months at sea. Hard as that may have been in the past, today climate change and high fishing pressure have made it even more difficult. The Conversation

For penguins in South Africa and Namibia, abundant supplies of their favoured prey, such as sardine and anchovy, are no longer where the penguins expect to find them. This causes the young birds to fall into what is known as an ecological trap. This is when they follow the usual cues to feeding grounds only to find that the sources of food in these places is no longer available. This can be due to changes in stocks of particular foods due to over-fishing or underlying environmental change

African penguins are listed as endangered by the International Union for Conservation of Nature, as numbers along their entire range in South Africa and Namibia have dramatically decreased in the last century and trends currently don’t show any sign of reversing. In the last 50 years, the population has dropped by 80% and there are only about 23 000 breeding pairs in the wild.

In our new study, we followed 54 juvenile penguins – penguins who have lost their down feathers and are now waterproof and ready to go to sea – on their initial journey along the southern African coast using satellite transmitters.

Dwindling fish stocks

The birds moved to areas of the ocean where sea temperatures are low and productivity – in the form of the phytoplankton microscopic food that is the base of many aquatic food webs – is high. To do so, they travelled large distances to areas such as St. Helena Bay along the West Coast of South Africa and Swakopmund in central Namibia. Both are historically known for their high fish abundance.

But large fish stocks no longer exist in these areas. This is because of the combined effects of the changing climate and fishing pressure. Since the lower levels of the ecosystem have not been affected in the same way, the signals that the penguins would have always used to locate their prey are still intact.

For example the phytoplankton is still there and is still preyed upon by zooplankton, microscopic animals drifting in the ocean. But today, the fish that would normally co-occur with their planktonic prey are scarce or absent.

Juvenile penguins are “tricked” into selecting the now poor habitat and fall into this large-scale ecological trap. This previously unnoticed ecosystem-wide phenomena explains the low survival chances of this endangered species, especially during its first year at sea. It contributes to the dramatic decline of the penguin population.

Modelling exercises in the current study showed that with sufficient food in these areas, the African penguin population on the West Coast of South Africa would be twice the size it is now. There would be around 5,000 pairs at Dassen and Robben Islands, instead of only around 2,500. Only juvenile penguins from the Eastern Cape colonies, located in Algoa Bay, foraged in an area which provides sufficient food, the Agulhas Bank.

In the last 50 years, the Africa penguin population has dropped significantly.

Escaping the trap?

Several conservation measures are being taken to halt the decline of the African penguin and a few could help get the penguins out of this ecological trap. Efforts to hand-raise chicks and create new penguin colonies may help bolster the population and build resilience against future change. The Southern African Foundation for the Conservation of Coastal Birds, South Africa’s largest rehabilitation centre, hand-rears several hundred chicks each year. This happens after they are abandoned in the colonies because their parents get oiled or injured, or simply cannot find enough food to raise them during the breeding season.

Once these birds reach fledgling age, they are released back into the wild. Fourteen of the penguins in this study were hand-reared and the results show that these chicks behave in the same way as counterparts raised by their parents. Unfortunately, these penguins also travel into areas with low food availability.

The chicks raised at the centre behave naturally once back in the wild and could be used as part of efforts to create new penguin colonies by releasing them at designated areas where they could found new colonies in closer proximity to the available food.

But a great deal more needs to be done to address the problem of the ecological trap. The study shows that large scale conservation measures – such as reduced fish quota or suspension of the fisheries once the fish population falls below critical ecological thresholds – are urgently needed to protect the endangered African penguin and other seabirds in the Benguela Current, a highly productive cold water system along the west coast of Southern Africa. These measures must go hand-in-hand with conservation initiatives that are in place already.

The ecological trap for African penguins was discovered by tracking juveniles. This is an age group about which very little is known in many seabird species. It highlights the importance of further studies on the survival strategies in the first year of particular seabirds’ life to understand the dynamics of species across their range.

Katrin Ludynia, Honorary Research Associate and Research Manager at SANCCOB, University of Cape Town and Richard Sherley, Research Fellow, Bristol Zoological Society and University of Exeter, University of Exeter

This article was originally published on The Conversation. Read the original article.

How the parrot got its chat (and its dance moves)

Many animals – including seals, dolphins and bats – are able to communicate vocally. However, parrots are among a select few that can spontaneously imitate members of another species. A study has now pinpointed the region in the brain that may be allowing this to happen – the region that is also involved in controlling movement. The finding could perhaps also explain the fact that parrots, just like humans, can talk and dance.

We know that birds that can sing, including parrots, have distinct centres in their brain supporting vocalisations, called the “cores”. But, exclusively in parrots, around these there are outer rings, or “shells”. Surrounding this is a third region supporting movement. This is an older pathway that is shared by vertebrates. To find out more about what the unique shell system actually does, the research team analysed the expression of genes in these pathways in nine different species of parrot. They focused on ten genes that we know to be more active in the song regions of birds’ brains compared to other parts of the brain.

They found that parrots, when compared to other birds, have a complex pattern of specialised gene expression in all three parts of its brain. That means that most of the vocal learning that is specific to parrots, such as imitation, must be taking place in the shell region and the part of the brain that controls movements. This is surprising, as previous work had assumed that only the dedicated core system would be involved in vocal learning and that the shells had nothing to do with talking.

My own research has shown that it is the connections between brain regions controlling cognitive and motor skills that support language in humans.

The researchers also examined songbirds and hummingbirds and found that the shell regions were indeed unique to the parrots. However, they said future research would have to clarify the exact mechanisms involved in imitating.

Imitation game

That this shell system is observed in so many species of parrot – including in Keas, the most ancient species known – suggests that the vocalisation abilities evolved around 29m years ago. For comparison, that is more or less the time when humans’ ancestors are believed to have branched off from other primates.

The researchers hypothesise that this shell structure evolved after the core system for singing in birds was duplicated in the brain, with the shell centre developing new functions such as mimicking. So studying the shell structure in parrots could help us identify other mysterious duplications that could have led to certain brain functions in humans.

Might be hard to believe but parrots have a lot going on upstairs.
Courtesy of Jonathan E. Lee, Duke University

Only parrots, humans and certain types of songbird can mimic other species. The fact that species as different as birds and humans share this behaviour is a clear example of “convergent evolution,” in which two species independently evolve structures supporting similar behaviours.

Imitation requires significant brain power and complex, specialised processes. For example, acoustic information must be represented, its organisation decoded and finally the sound reproduced. The complex specialisation of the core, shell and motor systems in parrots support these processes for imitation, enabling these species to couple auditory information from the environment with the finely grained behaviours necessary to produce them. There is currently no evidence suggesting that parrots have any special kind of articulators for producing spoken language. Rather, their brains seem to be doing the extra work.

Let’s dance

Interestingly, the authors also note that humans and parrots belong to another select set of animals – those that synchronise body movements to the rhythms of beats while listening to music. That is, unlike almost every other animal in the world, parrots and humans spontaneously dance (strangely enough, that group also includes elephants which have also demonstrated an ability to move along with music).

In parrots, such dancing is associated with the non-vocal motor regions surrounding the shell – which supports the possibility of a general capacity for learning regularities in the sounds they hear and coupling them with behaviour.

The study is a big step forward in our effort to understand what makes parrots so different from other birds. Indeed, the researchers themselves say they were surprised that the brain structures they discovered had gone unrecognised for so long.

The Conversation

Larry Taylor is Senior lecturer, Department of Psychology at Northumbria University, Newcastle.

This article was originally published on The Conversation.
Read the original article.