Speedy Species – Is it a Bird? Is it a Plane?

I couldn’t bring myself to watch the closing ceremony. The Olympics took over my life so much for 2 weeks that I wasn’t sure what to do with myself. And the constant BBC montages began to tip me over the edge. Roll on the Paralympics so I can spend more time watching these superhuman athletes smash world records, whilst I sit on the sofa taking on my own record – most chocolate digestives eaten in five minutes.

In my last blog I started exploring some of nature’s own record holders, with probably the most famous animal athlete of them all – the cheetah. Their small frame, strong legs, specialised muscles and super bendy spine mean these mammals are built for speed. But their 70mph sprint looks measly compared to the Concorde of the animal kingdom…

Kevin Cole from Pacific Coast (http://creativecommons.org/licenses/by/2.0)%5D, via Wikimedia Commons

The Peregrine Falcon

Generally, birds are built to be flying machines (which I’m sure isn’t news to you!) They have light, hollow bones, powerful chest muscles and that streamlined shape most speed athletes strive for (painful hair removal isn’t necessary for our feathered friends!) But there are many variations across different species and that’s where it gets interesting. Peregrine Falcons are designed to reach dizzying speeds. I’m sure you’ve all seen videos of these bird missiles shooting through the air as they perform their hunting stoop (if not, google it, you won’t be disappointed. Just make sure you don’t blink or you’ll miss it!)

The peregrine falcon normally flies at speeds of around 60mph but when it dives (or stoops) to attack it reaches 200mph! 200MPH?! How on earth doesn’t that bird pass out or, even worse, explode?!

Well thanks to the wonderful world of evolution, peregrine falcons are designed as intrinsically as jets (in fact– we’ve taken a lot of inspiration from the design of the falcon to manufacture planes!) Their slim feathers create the perfect streamlined silhouette when drawn against the body and attached to these are large flight muscles to help propel them through the air. The feathers also play an important part with video evidence showing small feathers popping up during the dive. Scientists believe these help reduce drag by keeping air flowing smoothly over the bird’s body – think about the flaps on the wings of an aeroplane.

By Aviceda (http://creativecommons.org/licenses/by-sa/3.0)%5D, via Wikimedia Commons

Perfecting your appearance to rocket you through the sky is all well and good – but your organs need to be able to keep up. Their circulatory systems are incredibly strong, with large lungs and specialized air sacs to take in as much air as a possible and a strong heart which beats over 600 times per minutes! And their muscles are stuffed full of red muscle fibres so they can take in lots of oxygen, increasing their metabolic activity to give them the flight power they need.

The change in air pressure resulting from a plummet of a 200mph dive is so large that it could and should damage the bird’s lungs. But luckily someone along the evolutionary path has thought of that. Peregrine falcons have small cone-like bones on their nostrils which guides the airflow away, reducing the air pressure and allowing them to breathe more easily in flight. This design is so good that it’s now used in jet engines!

By Ltshears (http://creativecommons.org/licenses/by-sa/3.0) via Wikimedia Commons

The thought of dropping through the sky this fast makes my eyes water. I’m sure anyone who’s ever skydived will tell you that it baffles your senses! Your eyes are dry but also streaming all at the same time and your cheeks wobble in a way you didn’t even know was possible (cue some great photo opportunities). So I’m really pleased to say these bird-shaped rockets have got that covered to. They have a third eyelid to spread their tears and clear debris as they dive – protecting their eyes as they keep them on the prize!

Their dive or stoop is so fast that it would actually be dangerous to grab their prey (normally other birds) out of the sky. So they’ve come up with a different tactic here too. They ‘punch’ their prey in the back of the head. Which is a much nicer way of describing what actually happens. In fact these birds use their terrifying talon to rip along the back of their targets neck, breaking their spine and causing them to tumble out of the sky. Lovely.

However awful an ending this is for the smaller birds that fall prey to these avian missiles, there’s no denying their strategy is a successful one – they’re found in every continent except Antarctica and around a fifth of the world’s bird species are on their shopping list. Impressive. But it’s not all about speed. There are other finely tuned athletes in the animal kingdom that have perfected other sporty skills. But more about that next time…

 

 

 

You Bird Brain

It has been a very (very, very) long time since I last sat down to write. I wish I had a valid excuse. The truth is, I have finally joined the real world and got my first grown-up, full-time job. This involves starring at a computer screen for 8 hours of the day and, unfortunately, when 5 o’clock strikes, I don’t want to see another screen until at least 9 am the following morning.

I have had a strong word with myself time and time again, each time promising that my next day off would finally be the day I get blogging again. However, the normal tasks of everyday life, and ITV3’s insistence on playing re-runs of Agatha Christie’s on Sundays, all keep getting in the way. 

BUT enough is enough. It’s approaching a year since I wrote regularly and that is, quite frankly, a little embarrassing. So, I’m here at the dining room table, trying hard not to ignore my laptop in favour of starring at my cat chasing birds in the garden. As clever and sneaky as Holly the cat may be, she is continuously outsmarted (and outmanoeuvred) by her feathered prey.

There is no denying that birds are a particularly clever set of individuals. There are a few examples of particularly cunning birds I have come across that I wanted to share. It’s examples like these that make me really wonder how anyone can be so sure that animals do not have a conscious ability to think. Let’s start with my sister’s favourite…

Herons

A Black-crowned night Heron, called Hank, to be more precise. We may take it for granted during our everyday lives but for evolutionists tool-use or, more generally, using a physical object to achieve a goal, is considered to be a bit of a big deal. Millions of years ago, when our ancestors first roamed the earth, using tools was a big evolutionary step. Whilst their tools were extremely basic compared to what we are used to today, looking at a seemingly ordinary object and seeing its potential to act as a spear or an axe has been interpreted as a sign of intelligence.

For a long while, we thought we were the only animals intelligent enough to make use of tools but this is definitely not the case. There are now countless extraordinary examples of animals using objects to reach their desired goal. The corvids, which includes birds such as ravens and crows, are particularly nifty tool users but it’s Hank the heron who’s definitely top of the class for me.

Hank has found an interesting way of using an object to help him catch his favourite fishy suppers. He lives on a golf course in Hawaii (very nice, for Hank), where visitors stand at the lake throwing scraps of bread for the ducks. Hank has been seen to steal a sneaky share of this bread, but he doesn’t eat it. He can be seen standing at the edge of the lake, dropping his bready bait and waiting patiently for the fish to flock. Hank noticed that it’s not just the ducks that enjoy this free meal; the fish in the lake are drawn to the surface to have a nibble as well. Unfortunately, for the fish, when they reach the surface, it’s not the golfers that have dropped the bread. Instead, they find Hank sitting with his bill wide open, waiting for his next unsuspecting victim.

Hank isn’t the only bird to use these nifty tactics to catch prey. There are currently 12 known species of bird known to use bait as a tool to catch fish, most of these are in the heron family. By using our afternoon visits to the park as an excuse to get their hands on some bait, we have unwittingly become their partners in crime. So, the next time you skip happily to the pond, feeling more Countryfile than Kate Humble, spare a thought for our fishy friends!

Honeyguides
I’m afraid this is another example where we have been used (but, not abused) by our feathery friends. Honeyguides are one of the few species of birds that feed on wax from insects. However, it is the behaviour of just a couple of species of honeyguides that gives the birds their name. One species employing this behaviour is the Greater Honeyguide. Top of the menu for our Greater Honeyguide is beeswax. Unfortunately, for these feathery creatures, it’s very difficult to get your beak on this tasty treat when it’s locked away in a robust hive protected by an army of angry bees. Luckily for the honeyguide, they aren’t the only ones who want what’s hidden inside these hives – we do too! The honeyguides have used this desire to solve their own problem. Honeyguides are given their name because they literally guide people to the honey! Once humans are at the hives they break them open and take the honey they want. Once they’ve got out of the way, the birds swoop in and fill their stomachs with the wax that’s left in the hive.

Drongos
It’s not just people that birds have used their intelligence to trick. Some birds have conned other species of bird into helping them survive. The pied babbler  is one species that has fallen for the Drongos’ charm. Drongos follow some groups of pied babblers and act as a protector. They’ve been seen to watch over a group and screech loud alarm calls to warn them when there’s a predator about. The pied babblers reward their knight in shining armour by allowing them access to some of the food they collect. I’m sure you’ll agree this all seems to mutually benefit both species. However, sometimes the food collected is not enough for the greedy Drongos. Occasionally, the Drongo has been seen to give false alarm calls, when there is no danger in sight, in order to cause the pied babblers to flee to safety. The Drongo then has free access to all the food it desires. This is called kleptoparasitism, where individuals attempt to steal food captured by others. The pied babblers have started to get wise to this and have been seen to scare Drongos off from their group, before they’ve had a chance to con them. However, there is no denying that those pesky Drongos are definitely a fine example of bird intelligence.

I’m sure you’ll agree these birds have all thought up some pretty inventive ways of keeping their bellies full. Of course, there are many more birds I could talk about. This is just a whistle stop tour of some of my favourite feathery tricksters.

 And, with that, I’m finally back. I’ll see you again very soon, I promise.

Putting Your Eggs in Lots of Baskets

Today is Mothering Sunday which made me think about all the lovely Mummies in the animal kingdom.  For our furry, feathery and slimy friends, child care can take many forms. In fact, in the animal kingdom caring for your children is not always a requirement.  Some animals, such as penguins, keep a watchful eye over their young until they are capable of taking care of themselves.  But others aren’t so attentive.  One particularly interesting example of animals with a more relaxed parenting style are the brood parasites – and my particular favourite are the birds.

Brood parasitic birds have removed their childcare responsibilities all together by laying their eggs in the nests of other birds.  (Note: the word ‘parasite’ usually makes people think of small, creepy bugs, but try and refrain from picturing these in this case.  Here the parasite is the bird trying to lay its eggs in another bird’s nest, otherwise called the host).  Think of it as hiring a nanny but without telling them or paying them for the service!  To us, this behaviour might seem slightly heartless, but for the brood parasite it’s a great strategy!  Sparing yourself the expense of rearing your own child means you can focus your energy on other things.  You have the time and resources to find new mates and make even more eggs, instead of having to defend your nests, incubate your eggs and feed your demanding chicks.

For the bird that’s left to bring up someone else’s young however, the story is very different.  In many cases the brood parasite will not only lay their egg in another nest, but will also remove one of the host’s eggs to do so!  Even when no egg is removed the host’s young are still affected, due to competition with the larger, more aggressive parasitic young.  Some parasitic chicks will even use a sharp spike on the end of their beak to crack the other eggs or even to brutally attack other chicks.

Obviously, the host bird has no interest in raising someone else’s child and so will do its best to make sure it doesn’t become a victim of these parasites.  This leads to the development of something called a coevolutionary arms race.  This basically means the host finds new ways to prevent itself becoming a victim of the parasite. Of course this just causes the parasite to develop her own ways of tricking the host into becoming her own personal nanny. This cycle has gone round and round in circles for centuries which means the birds have developed lots of neat (and pretty impressive) little ways to get their own way.  Let the battle commence.

A Reed warbler feeding a chick of a Common cuckoo

In the red corner, the Brood Parasite
Brood parasites can lay their eggs in the nests of birds from their own species or from a completely different species altogether.  Some will only parasitize a single host whilst others will parasitise a large range of different species – for example, the Brown-headed Cowbird has over 200 known hosts!  Laying your eggs in the nest of a female of another species has its problems – surely a Reed Warbler will notice when a baby Common Cuckoo hatches from one of the eggs it has been tending so lovingly? If a host realises an egg has been placed in its nest, it will remove it straight away.  There are several ways the parasite can try and stop this from happening…

It’s all in the timing
To begin with, you have to get your timings right.  It’s no good laying your egg in the nest of a bird that hasn’t started laying her own eggs yet – she’s bound to notice!  Studies have shown that parasites adjust their laying pattern to complement their hosts.  Although parasites need to lay late enough so their eggs aren’t immediately rejected, they also want their young to hatch first – this means finding the perfect balance between the two.   Many brood parasites have very short egg incubation periods and rapid chicks growth, giving them competitive edge over their new nestmates. 

Asian koel

In some species the males provide the females with a partner in crime.  Male Asian koels will distract female crows away from their nests to allow their partner to sneak to the crow’s nest.  Finding your opportunity can be tricky and once you’ve got it you can’t hang around at your hosts nest waiting to be spotted – otherwise your freshly laid egg isn’t going to last long.  Parasites have therefore adjusted the time it takes for them to lay their eggs, often only taking mere seconds to pop one out, meaning they can be in and out before the host notices.

Egg Mimicry

A Brown-headed cowbird egg in an Eastern Phoebe nest. Spotting the difference isn’t that hard in this case!

Getting your egg into a hosts nest is not where the story ends.  Bird eggs come in all different shapes, sizes and colours so a host can often spot an imposter.  This has led to the development of egg mimics.  Here the parasite makes their eggs look as similar to the hosts as possible.  This is particularly apparent in birds that parasitise specific hosts, as they can invest the time and effort needed into perfecting a mimic good enough to fool their host.  Studies have shown that all this effort to disguise your eggs is worth it – eggs that more closely resemble the hosts are much less likely to be rejected!

Common cuckoo eggs mimicking the eggs of a Reed warbler. The cuckoos eggs are the slightly larger ones.

In the blue corner, the Host
For the host it is definitely best to detect an intruder before you’ve invested precious energy caring for their egg.  Fighting off potential parasites is a start, but you must have a game plan for those birds that manage to sneak an egg past you.  Recognising your own eggs is a good place to start and evidence shows that hosts are able to do this.  If the host does spot an intruder, she will remove it from her nest.  Occasionally some hosts will completely abandon the nest – but this will only happen if the cost of finding a new mate, building a new nest and laying a new clutch is not too high. 

Accidentally rejecting your own chick is a big problem for the host.  If hosts struggle to identify their own egg, rejecting a suspected host at the egg stage can sometimes be too costly – just in case you accidentally destroy one of your own eggs.  Birds who fall victim to brood parasitism will often lay lots of eggs because of this – the more eggs you lay the more back-ups you have if you do accidentally destroy one of your own.  In these cases learning to recognise your chicks may also be a good strategy.  This involves learning to recognise the plumage patterns, begging calls and mouths of your own chicks – as the inside of some chicks beaks have distinctive patterns.

This battle doesn’t really have a clear winner.  Once one opponent finds a way to take the lead, you can almost guarantee it won’t be long until the other has found a way to edge back in front.  The struggle for survival means both birds will fight and fight until they are crowned the champion.  

It might seem like an unusual strategy but having their own free nanny service has allowed many bird species to thrive.  Just think of the cruises your parents could have gone on if someone else had paid for your upkeep!