A Common Tern

This morning at 06:40am a common tern, swallow-like and red-beaked, flew along the Kennet loop, eastwards past Reading prison.

I have occasionally seen common terns of the Kennet before. Once, I was with Zoe when one did a spectacular dive into the river and then flew up and off again.

Update on Wed 2005-07-06 by Tristram Brelstaff

On the following Sunday (June 24th) Zoe and I saw a lone common tern flying up and down the middle lake in Reading University grounds.  We saw it dive several times - the lake seems to provide better hunting than the river Kennet.  Each time it dived it did a sort of twist in the air before dropping down to the water.

A few days later I again saw the tern over the Kennet before 7am.  I suppose it is possible that all three sightings were of the same bird.

Natural Selection and Social Theory by Robert Trivers

When I first heard that this collection of papers by Robert Trivers existed I immediately wanted a copy.  I had come across Trivers' name and his ideas at second-hand many times in my reading over the past couple of decades but I had never read anything of his first-hand.  I had enjoyed William Hamilton's 'Narrow Roads of Gene Land' so much that the prospect of a similar feast from another leading evolutionary theorist was too much for me to resist, so I went out and ordered a copy.

'Natural Selection and Social Theory' contains 10 papers, each with a fairly substantial introduction.  I started by reading through the introductions and skipping the papers.   Within a week I was disappointed to find myself at the end, so then I turned back and read the  Reciprocal Altruism and Haplodiploidy papers more carefully. 

On the whole this is a lighter read than 'Narrow Roads': firstly, it is only 328 pages as opposed to 528+852 for the two volumes of 'Narrow Roads' and, secondly, Trivers' writing is less dark, intense and obsessive than Hamilton's. 

The introductions offer interesting side views on Ernst Mayr and Edward Wilson, people who, until now, I had known only through reading their books.  Trivers tells a story of how Mayr came to him in a dream and showed him the way to understand the relationship between queen and worker ants, and how Trivers later asked Mayr whether 'Personal communication' would be the way to acknowledge this 'help' in the paper!  There are tales too of Hamilton's legendary incompetence as a lecturer. 

From reading the introductions I also came to understand the significance of Hamilton's four-fold classification of social interactions into co-operative, selfish, altruistic and spiteful, something that had completely escaped me before.

Coots Building 'Second Nests'

Over the last week, I have on two occasions seen coots on the river Kennet building what appeared to be 'second nests'. 

The first time I saw this was when I saw one of the pair that had brought up two chicks on the nest near Highbridge Wharf started piling up strips of greenery under the boat traffic light just east of the Duke Street bridge.  The pair's two chicks seemed to be joining in, well one of them was standing on top of the pile.  At first I thought they had decided to move nest but after a day or so I saw that the new nest had disintegrated and they were back at their old nest again.

Then, this morning I saw that one of the coots from the nest at the mouth of Gunter's Brook was carefully draping strips of greenery over a log that had become fixed near the river bank.  It was placing the strips apparently quite deliberately, while its solitary chick looked on.

My first thought was this building of second nests could be the way that the parents teach their chicks how to build nests.  Another possibility is that these piles of greenery are food stores, however, this is less likely because there seems no reason to build them away from the main nest. 

Four Herons

This evening I saw four herons standing in a group on the west side of the lake near Frimley station.  They were only a few metres from each other.  Maybe they were a family?   One of them looked smaller and darker than the others.

Update on Fri 2005-06-24 by Tristram Brelstaff

Yesterday afternoon I saw three of the herons again on the lake near Frimley Station.  The small dark grey heron was stood by itself and then flew off.  Two other lighter grey ones were standing on another part of lake.

Carrion Crow taking an Ant-Bath

Yesterday I noticed a carrion crow (Corvus corone corone) behaving rather strangely on the lawn at the front of our flats.  It was sitting down in the grass with its wings slightly extended sideways, as if it was sunning itself -- but the Sun was not shining.  I though it rather strange, but I had other things to do, so I soon forgot about it.

Well, today, what I presume was the same bird was doing exactly the same thing but in a slightly different spot.  Then a car slowly drove past and the crow stood up and ambled further away from the road, waiting until the car was gone before returning to precisely the same patch of grass to sit down again.  Then it occurred to me that I had often seen ants in the grass down there, so I went downstairs to take a closer look.  Sure enough there was a concentration of ants in precisely the place where the crow had been sitting.  Presumably, the crow was using these ants to de-louse itself. 
When I came back in, the crow went back to the same spot to resume its ant-bath.

Update on Wed 2005-06-08 by Tristram Brelstaff

After observing the crow taking an ant-bath I started to think about how such behaviour could have developed.  How on earth did the crow learn that sitting amongst ants was a good thing to do?  After all, sitting down in grass is not something that crows do very often as part of their daily life, so they are not likely to have stumbled across this behaviour by accident, and I would have thought that their first reaction on seeing ants would be to eat them, not sit on them. 

Yesterday I realised that the obvious place that crows could sit amongst ants would be in the crow's nest.  Ants might seek out birds nests as good sources of small parasitic insects and scraps of food and maybe the birds have learnt the benefits of the ants' presence, to the extent that when they see ants on the ground the idea occurs to them that it would be good to sit down among them.  If this theory is correct then it would imply that ants must climb all the way up to crows' nests which are normally located in the tops of tall trees.  Does any one know whether ants are commonly found in crows nests?

Update on Sat 2005-07-23 by Tristram Brelstaff

As I am typing this I can see a crow taking an 'ant bath' on the lawn at the back of our flats.  It has been there for the past 15 minutes at least.