January 2013 - Page 2 of 2

09/01/2013

On a wing and a prayer

As someone who regularly requires the use of wild birds in my research, I often worry that the methods of capture and subsequent identification I use might in some way impede the individuals I capture upon release. I use wild blue tits (Cyanistes caeruleus) which I identify by means of a metal ring in conjunction with a unique combination of colour rings. Ringing has been used as a method of bird identification since 1909 when the first bird, a Lapwing ( Vanellus vanellus), was ringed in Aberdeen. Since then ringing has become one of the safest and most commonly used method of identification of wild-caught birds and as such has been an invaluable tool for the study of bird populations. One only has to look at some of the data collected by ringers on the age of some birds to be astounded by how long some individuals survive, information which would be extremely difficult to come by without the use of rings.

More recently however, other methods of identification have become increasingly popular, which are used in conjunction with ringing. Perhaps one of the most well known would be the use of wing tags, which are currently in use with the reintroduced Red Kite (Milvus milvus) here in Ireland, which I might add has been a huge success thus far. Yet data published in a recent study by Trefry et al. 2013 suggests that for some species the use of wing tags can be detrimental. Trefry et al. Studied the magnificent frigatebird (Fregata magnificens), a spectacular sea bird which is unusual in many ways not least for the fact that as a species that forages at sea they make every effort never to land on the surface of the water. In this study the researchers compared the effects of various methods of identification and measurement taking on the reproductive success of the birds. What they found was quite alarming, individuals which were simply ringed fared no different to individuals which were untouched by the researchers, but those which had wing tags added reared significantly fewer chicks to fledging. The reasons for this are as yet unclear, perhaps the addition of the tags impairs the aerodynamics of the wings to such an extent that tagged adults are less proficient foragers and therefore unable to meet the nutritional demands of their young.

There are more examples cited in the study by Trefry et al. which highlight the negative effect of such tags on other species of bird (as well as those on which they have no effect), which makes it clear that more research is needed in this area, to my knowledge no such study (and correct me if I’m wrong) has been carried out for our reintroduced red kites so one would hope that they are not doomed to fail before they begin.

Author

Keith McMahon: mcmahok[at]tcd.ie

Photo credit

wikimedia commons

07/01/2013

City slickers

Typically, when humans and wildlife meet it’s curtains for the latter. Think of all the megafaunal extinctions in the past and the mounting evidence that we’re responsible for an ongoing sixth mass extinction event. Aside from directed extermination we can change the environment over a very short time-scale to suit our needs and other lifeforms are often left playing catchup. This is especially true for plants and animals (microorganisms have such short turnovers that we don’t really impact them in this way); the plight of the blue swallow isn’t top of an industrialist’s list of priorities.

Despite these radical changes, some species have adapted to living in our towns and cities. This has piqued the interest of scientists and we’re now seeing the burgeoning field of urban ecology populated by urban ecologists. The amount of urban biodiversity is quite surprising and the adaptations of the flora and fauna comprising it equally so. Look at the previous post talking about birds lining their nests with material from discarded cigarette butts.

As civilization has developed we’ve become more aware of the value of nature, be it an intrinsic worth or a more practical value. So we can actively change our urban centres to accommodate more species if and when we choose. Sushinsky and colleagues asked how we should grow our cities in order to minimise their biodiversity impacts. Their conclusion was a more concentrated city plan would be better suited to avian diversity than a sprawling one. Certainly, it seems better for our cities to grow vertically rather than horizontally if we are to minimise humanity’s footprint. So, more New Yorks and fewer Los Angeles.

We can even provide supplementary food to animals. Fuller et al. showed that bird feeders can increase the abundance of birds and pointed out that up to a third of households in Australia, Europe and North America supply food for birds.

Then there are species that can prosper on our discards when it hasn’t been our intention to feed them in the first place. Badgers, foxes, raccoons, bears, the list goes on. All of them can make a living in an urban setting.

With more and more of us cramming ourselves into cities we should be aware that there are real benefits to interacting with nature. We feel psychologically better when there is more of the natural world around us.

To butcher Gordon Gecko, green is good.

Author

Adam Kane: kanead[at]tcd.ie

Photo credit

wikimedia commons

03/01/2013

You’re grounded!

Pterosaurs are the largest animals to have ever flown. Some species had wingspans exceeding 10 metres dwarfing the largest avian challenger. It must have been quite a sight to see one of these things blocking out the Mesozoic sun. But there have been niggling doubts about the ability of the larger representatives to fly. Will we have to re-evaluate our mental image of the Mesozoic and ground our pterosaurs?

Flight is no easy thing for an animal. It makes all sorts of demands on the physiology, morphology and ecology of the creature trying to take to the air for a living. With every added kilo a bit more lift has to be generated, for every extra wing flap more energy is required. Still, most pterosaurs look like they fit the bill. Their skeletons were heavily pneumatized and they had a hyper-elongated fourth finger from which they could support a membranous wing.

The problem arises when we look at the giant pterosaurs especially the Azhdarchidae family which houses the biggest species like Quetzalcoatlus northropi and Arambourgiania philadelphiae. One analysis gave a mass estimate of half a tonne for Quetzalcoatlus n., which would almost certainly render it flightless. Other researchers point to the terrestrial adaptations seen in this family and of course we can see many instances of birds who have become secondarily flightless. A size gap was pointed out where there exist small pterosaurs and giant ones but no intermediates which was said to mirror the pattern of flying birds and flightless ratites. Then there is the taphonomic bias seen in the fossil record whereby most of the Azhdarchid skeletons are found in terrestrial environments.

But not all palaeontologists are convinced by these arguments, pterosaur specialists Mark Witton and Michael Habib have taken each one of these lines of evidence to task and found them wanting.

Firstly, while most of the fossils have been found on land this doesn’t mean the animals were terrestrial, many bird species fly exclusively over land, so that bias is neither for nor against.

Secondly, the suggested size gap looks like an artefact in the fossil record which has been filled with intermediate forms.

Perhaps the most convincing piece of evidence in favour of flightlessness are the huge mass estimates. A half tonne reptile is going to struggle to get airborne. But this figure is beginning to look like an overestimate, the result of distorted fossils and inappropriate scaling techniques. A more lightweight figure of 240 kg looks to be more realistic when these biases are accounted for.

What of the terrestrial adaptations? Well, there is no issue with the animals being adept on the land while still being able to fly. Indeed the authors above argue that large Azhdarchids occupied the niche of modern day ground horn bills or storks both of which are well adapted to the land while still being able to fly.

In the end it looks like giant pterosaurs did take to the skies. Piecing together the mode of life of long extinct species is never easy but it’s not impossible.

Author

Adam Kane: kanead[at]tcd.ie

Photo credit

Witton MP, Naish D (2008) A Reappraisal of Azhdarchid Pterosaur Functional Morphology and Paleoecology. PLoS ONE 3(5): e2271. doi:10.1371/journal.pone.0002271

02/01/2013

A year of discoveries – 2012

With the end of the year and the inevitable onslaught of re-edited best of 2012 countdown shows, I decided to join the year’s long nostalgic trip with a look at some of my favourite scientific discoveries of 2012. As the obvious breakthroughs such as the Higgs boson etc will be covered ad lib elsewhere I decided to stick to topics more closely related to my field and in line with the blog. So here’s my short and erratic list, enjoy.

As a region that is less explored then the surface of the moon, especially after the success of the ebb and flow gravity mapping satellites, deep sea environments show no slowing down in throwing up new discoveries and 2012 was no different. While James Cameron has stolen all the headlines with his record setting trip to the ocean floor, it’s the discovery of a new hydrothermal vent community in Antarctica that makes my list. The Vent system, an ecosystem supported based on bacteria that chemosynthesis and obtains its energy independently of the sun, was found to include a new species of yeti crab and an assemblage of species markedly different from other vent systems. The discovery of the new systems and its marked difference to other vent systems may help us further understand the biogeography and the dispersion and colonisation of such isolated and extreme environments.
Amongst the fantastic successes in space exploration this year included the mapping of the moons surface, the discovery of evidence of water on the asteroid Vesta by Dawn and of course the landing of the mars rover Curiosity. However perhaps one of the most unexpected discoveries of the year came from the most inhospitable of planets Mercury. Despite being the closest planet to the sun were temperatures can reach a searing 400 degrees Celsius at the surface the Nasa found evidence of water and organic compounds at the bottom of a crater near the poles, which is permanently shaded. While life would not be expected to be found in such an inhospitable location it points to the ubiquitous presence of water ice and organic materials throughout the solar systems, a pre-requisite for life on this planet.
With an estimated 86% of the earths species awaiting to be discovered, 2012’s batch didn’t fail to disappoint. Amongst the most notable new species to science include two new species of monkey (Cercopithecus lomamiensis the first to be found in Africa in 28 years and Nycticebus kayan a venomous slow Loris found in Borneo), the smallest know reptile, the largest fossil penguin species and the 126 new species found in Mekong basin just to name a few. Also worth nothing, although not a new species, is the spade toothed beaked whale skeleton, a species yet to be seen in the wild, which no evidence of its existence was known for 30 years.
While probably not the most talked about scientific advancement of the year, a paper in Nature by Sugihara et al explaining a method of unravelling causation was one of the most talked about in this department. The statistical procedure called convergent cross mapping can determine cause and effect problem in complex data such as fisheries population dynamics, a problem that so often pains ecologists. While a statistic method doesn’t usually get the excitement levels up but this method will likely provide numerous insights into ecological systems in the future.
To counter balance including a statistical paper in my festive highlights of the year I decided to include the several instances of what seems to be reverse Doolittleism, animals trying to speak back to us. While parrots ands primates are usually the mainstay of investigating language, it was a beluga whale and an elephant that caught the ears of scientists this year. Noc, a captive beluga whale in the marine mammal foundation in San Diego was reported to have produced such a convincing human voice that handlers in the water surfaced to say “Who told me to get?”. Furthermore the whale was trained to speak on cue by using much lower sound waves than the normal high click sounds of beluga whales. A second incident of an animal attempting to mimic human language was Koshik, a male elephant in Everland theme park in Yongin, South Korea. Koshik can imitate words such as “annyong” (“hello”), “anja” (“sit down”), “aniya” (“no”) and “choah” (“good”). While other animals have been known to imitate human language, the addition of such large charismatic animals that are both intelligent and also unknown to normally imitate sounds, such as birds do, may be an important input into the evolution of vocal learning.

That’s my list of my favourite discoveries of 2012, which is by no means comprehensive, for example take a look at the wiki page of science in 2012 for a day-by-day list of the best discoveries of the year. Lets hope for the same in 2013.

Author

Kevin Healy: healyke[at]tcd.ie

Photo credit

wikimedia commons