Archives for the month of: July, 2012

I’m pleased to say I now have data from over 500 individual pigeons from various locations throughout the UK. Thanks to everyone who kindly submitted details of their local flock.

The data, shown below, has confirmed research that has been conducted previously but leaves many unanswered questions. It also shows how interesting feral pigeons are to study.

Image

Of the 503 birds, 58.96% show the checker plumage type whilst 25.24% show the wild type or ‘blue bar’ plumage.

There are many theories as to why this may be the case, for example, it has been found that checker birds have an extended breeding season over the wild type birds, as they do not show the gonadal regression found in the blue bar birds. Gonadal regression in the winter months has been found to be linked to the ability to store fat for surviving in times of food shortage and cold weather.  Such an ability would be essential for wild rock doves with seasonal variation in nutrient availability. However, feral pigeons are far less subject to fluctuation in food availability and therefore, gonadal regression may be less of an advantage.

Interestingly, it has been found that city living blue bar birds have higher lead and cadmium levels than checker birds – despite the banning of leaded petrol, cadmium is readily found in car tyres and is deposited on roads and curb sides. Such contamination may possible effect the breeding success and health of blue bar individuals.

Equally, female mate choice may be playing a part, which is something I hope to research in the near future.

Thank you again to everyone who has helped… please keep those results coming in. I’ll also need more help in the near future with some more in depth pigeon spotting.

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A massive thank you to UK and Eire Natural History Bloggers for kindly adding me to the network. 

They have some fantastic bloggers on a wide range of subjects, to check them out, please visit:

http://uknhb.blogspot.com

 

Time for a quick update…

So far we have details of 242 individual pigeons from 4 locations. Early results are certainly interesting!

Of these pigeons, 62 show the blue bar (wild type) plumage, but 112 show individuals show the chequered (or check) plumage. This is interesting as the blue bar phenotype is dominant over the chequered phenotype. It would be more likely that a blue bar plumage would be inherited and expressed in an individual than the chequered plumage, so these results are not consistent with this. It may be that having a chequered plumage may be more beneficial to an individual than a blue bar plumage.

Clearly, these results could be due to lack of data – hopefully more results will bring greater clarity.

So, if you’re out and about, please count your pigeons!

For more info, please see my last post: Let’s get pigeon spotting!

Thanks again to those that have sent in their results.

My last post, variety is the spice of life, explained some of the wonders of pigeon plumage. In order to investigate the mechanisms behind the variety of beautiful colours we see today, it is important to see if there are any trends throughout the UK. My recent move to Cornwall found me noticing that there are far more pied pigeons there than 200 miles west in the city of Bath.

To get a detailed picture of just how varied pigeons are in different locations, I need YOUR help.

I’d like as many people as possible to count the pigeons in your local flock, and note down the number of each different colour type that you see. It would be great if the time, date and nearest town, city or village could be noted too. Below you will see pictures of some of the most common colour morphs you are likely to see.

As an example, your results may look a little like this:

Date: 12.07.12

Time: 15:30 –

Location: Bath

Total flock size: 50

Number of blue bar: 30

Number of chequers: 10

Number of pied: 5

Number of red: 5

If you spot any pigeons that don’t quite fit the varieties seen below, they can be simply recorded as ‘other’.

Don’t worry if your numbers aren’t perfect, especially as pigeons strut around so quickly it can be tricky to know where one bird ends and the next begins.

You can send your results by email to pigeons@gmx.co.uk or by filling in the form at the bottom of this page.

Thank you very much for your help, I hope you enjoy pigeon spotting!

One of my biggest fascinations when it comes to feral pigeons, is the wide variety of plumage types they show. The plumage a pigeon shows, is known as its phenotype and the genetics behind the plumage is known as its genotype. When we consider most other species of bird, such as starlings (Sturnus vulgaris) all adult birds appear to be a similar colour, yet feral pigeons come in a wider array of different colours and patterns.

Blue bar

This pigeon shows the blue bar phenotype – this is the closest to the wild type phenotype shown by the rock dove

Feral pigeons are descended from domesticated pigeons, that have escaped and learned to live in the wild once more. Through domestication, a wide variety of different colours and shapes were produced from the grey ‘blue bar’ colouration of the wild rock dove the domestic pigeons were produced from.

The differing plumages feral pigeons display not only look beautiful but are very interesting to scientists. Most feral animals (animals living wild but descended from domestic stock) when free to choose their own mates and to breed freely, over time, eventually come to resemble the ‘wild type’ phenotype. Many people believe dingos ( Canis lupus dingo) once derived from ancient domestic dogs, have undergone this process (known as reversion) to become the uniform sandy colour they now show.  Although feral pigeon flocks are often supplemented with escaped fancy and racing pigeons which may be of a range of colours, it is thought that the proportion of non-wild type coloured pigeons in feral flocks could not be maintained by addition of these birds to the gene pool.

This checker pigeon can be identified by the specks of dark colour on the wings, this is different from the blue bar shown above. 

There are many theories as to why this variation is maintained or why this variation shouldn’t be maintained, and I hope to be able to look into these further:

1) Predation – Many believe that avian predators tend to target the ‘odd one out’ in a flock such that a white bird in a flock of grey birds may make an easy target. If this is the case, this should impose a selective pressure against these non wild type plumages. I hope to investigate this issue further to see if this is true.

2) Mate selection – It is thought that pigeons may use plumage colour as a means of choosing a mate. Mating with individuals different from oneself is a good method of preventing inbreeding. If this is the case, what criteria do the birds use when selecting a partner?

3) Fitness advantages – It is thought some plumage phenotypes show improved fitness, however, if this is the case it may be thought that non wild type plumaged birds should make up a greater proportion of the population than they actually do. Or, could it be that an equilibrium has been reached with any fitness advantage being balanced by a possible fitness disadvantage in terms of predation risk?

Red

The red phenotype is surprisingly common given how different the birds look when compared to the wild type birds

These are just a few of many questions to be asked on plumage variation in pigeons and I believe we have a lot to learn.

In order to look into these questions I’ll be needing YOUR help.  I’ll be posting for help on this blog really soon.

One of the joys of the natural world is its unending variation. Most variation is easily understood, such as the webbed feet of water birds but others leave us asking, “why?”

My question for today is, why do wood pigeons (Columbar palambus) have unusually shaped pupils?

Here is a photo of a wood pigeon:

Image

Note the shape of the pupil of this wood pigeon (Columbar palambus)

Compare the pupil of the wood pigeon above with that of a feral pigeon (Columbar livia):

Feral pigeon pupil

The pupil of a feral pigeon (Columbar livia) is round.

 

Normally google is a wealth of knowledge, yet when it comes to finding out why there is such a difference in pupil shape it draws a blank.  If you can shine a light on this, please get in touch.

Following on from my last post, I wondered exactly how many pigeons could be supported with some of the most common fast food items. In order to calculate this, we need to know the calorie requirements of the average pigeon. Rough estimates place this at around 80-100 calories per day.  It can be hard to give an accurate figure as requirements change with age and breeding status. Clearly there are many macro and micro nutrients required by all living creatures to thrive, however, when considering calorific requirements, it is possible to easily calculate the number of birds a food item could support.

Would you like fries with that?

Pigeons are adaptable birds and will try most things once. The question is, how does this effect their productivity?

The big mac burger contains 490 calories, enough to provide sufficient calories for around five adult pigeons.

Similarly, a large fries contains 330 calories, supporting three adult pigeons.

Given the high calorie density (a measurement of the average calories per weight) of fast food, it is not difficult to imagine that large flocks could be maintained with only a small volume of such food available.

A large fries contains 330 calories, supporting 3 adult pigeons.

However, avian fat metabolism appears to work differently. The majority of stored fats, such as that stored in the muscles called upon for sustained bouts of flight, is composed of fat produced by the liver from assimilated carbohydrates. In fact, studies of pigeons injected with a glucose solution showed rapid fatty acid production, with all glucose metabolised by the liver within 15 minutes.  The addition of a large quantity of fat to the diet actual reduced the fat synthesised by the liver, potentially reducing the stores of fat available to the bird.

Therefore, could the high fat content of modern fast food actually be reducing feral pigeon productivity, despite offering greater ease in meeting calorie needs? Or will natural selection result in pigeons with modified fatty acid synthesis?

106.5 million pigeons could be sustained by customers dropping just a quarter of each burger sold.

As a side note, in 2010 87 million big macs were sold. If only a quarter of each of these burgers was to be dropped on the floor, 106.5 million pigeons could be sustained for a day!

Patterns of Lipid Storage and Utilization in Birds, Charles R. Blem. American Zoologist , Vol. 16, No. 4, Lipids in Animal Life Histories (Autumn, 1976), pp. 671-684

Pigeons appear to have an uncanny ability to defy all attempts at eradication by people who mistakenly believe they are a risk to human health.  In order for a population to remain stable, each pair need only produce two surviving offspring to eventually replace themselves. However, no individual can know the probability of any of its offspring surviving and therefore, must attempt to produce as many offspring as it can. Feral pigeons show iteroparity, that is, multiple breeding attempts over a life time and are known to pair for life. As R selected organisms, feral pigeons can respond quickly to favourable circumstances, producing offspring in a short space of time, which in turn can breed within 6 months.  In fact, the strong pair bond of adult birds allows clutches to overlap, with the female sitting on a new clutch of eggs whilst the male tends to the newly fledged youngsters.  Clearly, this highlights the very reason lethal control methods are ineffective.

Young feral pigeon

Feral pigeon youngsters look very similar to the adults – the beak and eyes often give the game away. Youngsters also squeak to the adults, hence young feral pigeons are often referred to as squeakers.

Schein’s 1954 study of feral pigeon recruitment found interesting results. Two sites were studied, a church steeple with multiple nesting platforms and a hospital. Nests were monitored from point of lay to fledging and the number of fledged young was recorded. The majority of the nests on the hospital study site were located within a central heating tower where temperatures remained warm and stable, whereas the ambient temperature of the church site fluctuated,  however, results showed very little difference between the survival probability of both flocks.

Of 152 eggs laid at the church site, 85 hatched, and of these, 47 fledged , giving a fledging probability of 0.309.

Similarly, of 293 eggs laid at the hospital site, 149 hatched and of these, 83 fledged giving a fledging probability of 0.283.

Given that temperature was shown to have little effect on the fledging probability of individuals of either flock and that both flocks showed similar figures, it can be suggested that other causal factors are involved.

Which brings me to the strange title of this blog…

Given the r selected nature of feral pigeons, food is a factor in the rate of offspring production, so I wonder how the changing face of the human diet affects this rate.

The fact that we are eating greater amounts of fast food is not in question, obesity levels have rocketed since this study was conducted. In 1950, 9.7% of Americans were obese, compared to 30.5% today.  Has the food available to feral pigeons today subsequently increased in both quantity and calorific content? If this is the case, what effect has this had on the probability of offspring fledging today in comparison to those in 1950?

A repeat of this study today may yield interesting results as it may be found that our increasing demand for higher calorie, convenience foods is causing a subsequent increase in one of the most adaptable species on the planet.

REF

Schein.W (1954) Survival records of young feral pigeons, The Auk,  Vol. 71, No. 3 (Jul., 1954), pp. 318-320

Hi everyone,

 

As this is my first post, I thought I’d start with a picture of a particularly beautiful individual photographed in the equally beautiful city of Bath, UK.

Needless to say my next post will be far more on task!