Cormorant question

[StevieEvans]

Question.
What 'type' of feet do Cormorants have?
I presume they are webbed, but how can they perch in 'flimsy' type trees?
Question.
What sort of population change have you experienced over the past ten years?
Question.
I heard somewhere that these 'new' inland populations are continental birds? is this correct?
Question.
How much (in weight) does an average Cormorant eat per day?
Any ideas.
Stevie.

[christineredgate]

Stevie,I do hope someone can answer your questions.We have lots of Cormorants here.They perch on poles in the sea,they perch for hours on some dead tree trunks in the Lagoon,they sit on the shore line fanning their wings,fascinating birds.
Christine.

[alan_rymer]

Steve

As an angler I did make it my business to find out something about them:

Question.
What 'type' of feet do Cormorants have?
I presume they are webbed, but how can they perch in 'flimsy' type trees?.Heavily Webbed
Question.
What sort of population change have you experienced over the past ten years?.Locally from 0 to about 50 or 60. Most counted at any one time/place was 48
Question.
I heard somewhere that these 'new' inland populations are continental birds? is this correct?. Believe they originally came from the Inland continental waterways, Belgium etc.
Question.
How much (in weight) does an average Cormorant eat per day?
Any ideas.
Stevie.The late Chris Mead told me 400-450 grams per day

[IanF]

Definitely webbed.

[Jane Turner]

I've seen them perched on high tension cablees... never seen them land though, I imagine that is the hard bit!

[IanF]

I've seen them landing on some pretty thin braches in the tops of tall trees, at Low Barns actually Stevie in the tops of the tall trees to the right of the island from the south hide. They don't seem least bothered when the branch drops four or five feet before rebounding. They just hang on and then settle down. Sometimes two or three perch together like this.

[Michael Frankis]

The re-colonising inland populations in Britain are made up of a mixture of of Atlantic race (carbo) from the coast and Continental race (sinensis) from Holland, etc., interbreeding freely.

Note re-colonising. This is not a new phenomenon - there is plenty of historical evidence that Cormorants used to be widespread inland breeders in the past, before the invention of accurate guns made them easy to kill off (circa 1750-1800).

Cormorants also have a long evolutionary history of nesting in trees; just because a foot is webbed, doesn't mean it can't perch on a branch! May actually give it a better grip.

Michael

[StevieEvans]

Hi, Many thanks for all replies.
Been watching birds roost at Durham (BrassPond) last few weeks
They all sit on islands made of pallets, then at dusk take to the air before going into roost trees.
The trees are Silver Birch approx 35'-40' on an island. To see these birds trying to land is comical, the adults seem to have it sussed out & aim for the more substancial branches with less flex, kind of stalling just before landing.
The younger birds on the other hand very often 'crash-land' falling through the branches! Sometimes knocking off their neighbours, some try to grab branches with their bills while falling!

I wondered if the continental inland breeding birds had differently developed feet & 'gripping' toes?, as some birds seen to land & hold quite effortlessly.
As Ian says branches often sway quite violently, but the birds try their hardest to hang on.

As for population/numbers, the pond here isnt huge, but is in the fly-way of the River Wear valley.
10 year ago the max recorded was 12 birds, but mostly only 5-8 seen. (tree roosting was Not carried out then at site)
Now there are up to 38!! birds roosting each night. Quite a large % increase. The trees are showing signs of distress due to the numbers involved.
Over the same time period the site has lost 4 breeding pairs of GCGrebe, previously being the main colony in the County. (this may well be due to loss of nest sites though) Although 38 birds X 400grams = lots of fish!

On the whole i think its our 'common' birds which are often the most interesting, but perhaps overlooked...? Stevie.

[StevieEvans]

MF
Had not realised it was a re-colonisation.

Wasn't there was a lot of talk to it being linked to decline in N.Sea fish stocks..?

What do you think has triggered the return of them inland?
Stevie.

[Michael Frankis]

Hi Stevie,

I doubt the Cormroants are responsible for the decline in GCGrebes, they eat very different size fish - in fact, cormorants could help grebes by eating some of the larger predatory fish that are eating the same size fish that the grebes eat.

What triggered the return inland - reduced persecution.

Wasn't there was a lot of talk to it being linked to decline in N.Sea fish stocks..?More nonsense from the militant wing of the Angler's Federation ;)
The decline in North Sea fish stocks is due to human overfishing, no more, no less. One trawler can catch as many fish in a day, as a thousand cormorants eat in a year.

Michael

[DoveKeeper]

I watched a cormorant surface next to my boat with a Winter Flounder that I was sure was too big to swallow. I was wrong. It seemed to be stuck in it's throat for a time but the lump soon disapeared.

[alan_rymer]

Hi Stevie,

I doubt the Cormroants are responsible for the decline in GCGrebes, they eat very different size fish - in fact, cormorants could help grebes by eating some of the larger predatory fish that are eating the same size fish that the grebes eat.

What triggered the return inland - reduced persecution.
Quote:
Wasn't there was a lot of talk to it being linked to decline in N.Sea fish stocks..?

More nonsense from the militant wing of the Angler's Federation ;)
The decline in North Sea fish stocks is due to human overfishing, no more, no less. One trawler can catch as many fish in a day, as a thousand cormorants eat in a year.

Michael

Errr Micheal

I think he meant that the decline of North Sea fish stocked caused by overfishing drove the cormorants from the North Sea where they would normally get their food!.

Maybe that was the original reason but I doubt it. Now the living in the Inland Waterways has proved easy. Aand they've grown soft!.

[Daz]

MF


What do you think has triggered the return of them inland?
Stevie.
Large supplies of easy to catch food. One lake I fish on, which is 4 acres, used to get 10 cormorants a day on. As a result, the following summer very few small fish were caught, and by that I mean 1lb plus roach. The only things that seemed to survive were the large carp. Cormorants eat FAR more fish than what predators like, say, Pike eat. Saying that our resident G.G. Grebes still find plenty to eat. I firmly believe it is the overfishing of our seas is what drives a Cormorant inland. I think Cormorants are here to stay, and that is bad news if you are an angler.

[alan_rymer]

Large supplies of easy to catch food. One lake I fish on, which is 4 acres, used to get 10 cormorants a day on. As a result, the following summer very few small fish were caught, and by that I mean 1lb plus roach. The only things that seemed to survive were the large carp. Cormorants eat FAR more fish than what predators like, say, Pike eat. Saying that our resident G.G. Grebes still find plenty to eat. I firmly believe it is the overfishing of our seas is what drives a Cormorant inland. I think Cormorants are here to stay, and that is bad news if you are an angler.
Daz
These Cormorants were working the inland waterways the other side of the channel, they have just crossed over and extended their range much as the Collared Dove has extended its range. I don't think overfishing of the sea's has affected this race of Cormorants much at all!. How much have the other fish eating seabirds been affected?. When was the last time you saw a Gannet fishing in your local pond.

[Daz]

Good point Alan.

[John P]

When was the last time you saw a Gannet fishing in your local pond


Do Gannets eat freshwater fish?

[Daz]

I don't know, I have never seen one on a freshwater lake or river.

[alan_rymer]

Do Gannets eat freshwater fish?Do Gannets not eat Freshwater fish?.

Pedants Anonymous

[tony.hetheringt]

I've read somewhere that cormorants and shags are some of the most ancient of birds.
I suppose they do look a bit dinasaurish. However if this is true, what happened to natural selection? Why haven't they developed more waterproof feathers,that don't need spreading out to dry? Auks,ducks,grebes or divers don't need to do this.
regards Tony

[Michael Frankis]

Hi Tony,

They 'deliberately' don't have waterproof feathers (more accurately, have evolved not to). If the feathers get wet, it means they don't trap any air when they dive. That means they can dive deeper, faster, and chase fish more efficiently, because they're not having to fight against the buoyancy of air trapped in their feathers.

The downside is that they need to eat more food to supply the body warmth when living in cold water. But it is still a successful strategy.

Michael

[Bluetail]

I thought no one was really sure why Cormorants held out their wings. Certainly some doubt that they do it to dry them - especially since they've been seen doing it in the rain. I even saw that myself once (at Radipole). There used to be a suggestion that the wing-spreading was perhaps to aid digestion. Not sure that theory was ever very popular and I haven't kept up with the arguments.

[Michael Frankis]

Hi Jason,

They'll hold their wings out in the rain, and they'll also hold their wings out even when they've caught nothing and have nothing to digest.

Let's face it, they are FISHERMEN . . .















"You should've seen the one that got away . . .


it was this big . . . .



HONEST!!!"

[mike60]

Maybe no one told the cormorants that drying their wings in the rain doesnt really work :-)
Animals in nature often behave in set patterns, even when its innaproriate to do so.

[Keith Reeder]

Cormorants do present some interesting dilemmas, don't they?

As a birder, it's hard not to be impressed by the critters - they are clearly filling their niche very effectively, and I enjoy watching them immensely - common birds or not.

But as a(nother) angler, I can't help but resent the same birds for eating "my" fish!

Of course, there has also been an (apparent) increase in the numbers of other fish eating birds in this part of the world - goosander seem to becoming seasonally as common on some rivers as herring gulls - and I wonder what might be the cause of that influx - assuming there has been an actual increase, and not simply the paranoid imaginings of worried anglers!

I actually fish the "Brasspond" mentioned by Stevie Evans and hadn't realised the cormorant presence was quite as significant - I'll have a closer look next time...

[tony.hetheringt]

Hi Tony,

They 'deliberately' don't have waterproof feathers (more accurately, have evolved not to). If the feathers get wet, it means they don't trap any air when they dive. That means they can dive deeper, faster, and chase fish more efficiently, because they're not having to fight against the buoyancy of air trapped in their feathers.

The downside is that they need to eat more food to supply the body warmth when living in cold water. But it is still a successful strategy.

Michael
Hi again Michael,
If I say the word penguins, should the same not apply,or do penguins have
feathers and/or blubber?
Regards Tony

[Michael Frankis]

Hi Tony,

They've gone down the other route - maximum waterproofing to maximise energy efficiency. So they're less adept at catching fish, but don't need to eat so much, either. Both strategies work, though the penguin/auk strategy is probably the better one in colder waters; cormorants evolved in warmer areas. They have also proved fairly successful in colonising cool waters, but not so well as penguins or auks. Equally, you don't get penguins or auks in warm waters, their strategy is less competitive there.

Michael

[tony.hetheringt]

Thanks Michael,I'm no longer dubious.
All the best Tony