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Re: Bird Behavior: A Discussion

Posted: July 11th, 2010, 9:51 pm
by ame
oh wow, Liis! you've done the thing that i have been dreaming about: you've checked their menu for the last year! :loveshower: Jürka has been checking the incubation period during last season, the same thing which i did for this year. after he began his work i started to think that our small research isn't actually quite complete without the investigation on the nestling time, that is the sharing of the feeding job between the parents and information of their menu items and feeding timetable. and now you have fulfilled my secret wish, at least to what concerns last season's data. :thumbs: :laugh:

how about joining our efforts and include the results of your investigation in our report? the last season's Pontu pictures are available in the internet (starting in as Techno-Urmas restored them there for Jürka's disposal.

Re: Bird Behavior: A Discussion

Posted: July 12th, 2010, 8:37 am
by Liis
Thank you, Ame! This was really only a very superficial and preliminary check!
But it seems that there are interesting questions, yes, and maybe worth a more careful look. I didn't even look at the delivery schedule: who, when, what - only remember seeing Mutikluti noting that Linda delivered big fishes a few times too.

The period from March 12 (eggs being laid) to mid-July (eaglets are outside nest), is about 125 days. Feeding frequency certainly varied with the eaglets' development, but 4 times a day as average for the whole period is probably not too high. With that the birds make up 2-3% at most of the menu.

In Tiit Randla's book "Eesti röövlinnud / Estonian birds of prey" (1976), prey for WTE is stated to be mainly waterfowl and fish. Mammals occur too but often as carrion and in winter.
From Estonia Tiit Randla mentions 5 species of fish (pike, perch, tench, crucian carp, eel - surprisingly no salmon?), 19(!) bird species, and 5 mammals (grey seal, deer, rabbit, squirrel, polecat (!)).

In Norway the food of WTEs was found to be on average 50% fish, 25% birds, 25% mammals (carrion), data still from Tiit Randla's book.

Camilla Ekblad published a graduate thesis in 2004, Nesting time diet of the White-tailed Sea Eagle in different archipelago zones on the Åland Islands (71 pp, Swedish with English summary). She found 80 diffferent species of prey. The main prey, except in the inner part of Åland (Ahvenamaa Islands) was birds (66%); in the inner part of Åland fish dominated (birds 45%).

Re: Bird Behavior: A Discussion

Posted: July 12th, 2010, 5:52 pm
by ame
btw: i found out that the date of the first eggs last season was in fact March 11th and not 12th as is frequently mentioned. the egg can be seen on the second video on the LK Merikotkakaameruutised (, just scroll down; it's the video right above the pig parade video: mms:// there at 9.44 Sulev rolls the first egg, a day before it's 'officially' noticed. i don't know why it's not seen earlier... :puzzled:
the first video with two eggs is there on March 14th at 10.40.

Randla's information about the Norwegian menu must be based on Willgohs' thesis. Willgohs collected pellets from the nests and below them and had the contents identified.
- i'll try to locate the Ekblad-paper, but if it is a MS-thesis then it's only in the exact university where the thesis was made. thank you for the reference! :wave:
edit: i managed to find it after some difficulty when i used the author's full name as a keyword. the title you gave didn't help because the original title was in Swedish! :D
it is a MS-thesis, as i guessed, and it's available in the University of Helsinki. i'll borrow it later it i think it's necessary. :nod:

Re: Bird Behavior: A Discussion

Posted: July 13th, 2010, 6:59 am
by Liis
The whole thesis is there on the Internet ... _gradu.pdf, as said, in Swedish but 1-page English summary.
A search with for instance "white-tailed eagle" ekblad in Google Scholar produces her work as first ref. (in 13 varieties, no less!) The title and abstract are also in English, and searchable in English by GS (I wouldn't have come across it otherwise); quite possibly it isn't there at all in regular Google.
But Google & co. are so huge, the search results we see are really not precise but a statistical selection based on some kind of fuzzy logic. Which is why one can search in vain for a perfectly valid hit found earlier, using the same words.

In a way Ekblad has used 2nd-hand material, i e pellet remains collected from WTE nests during inspections (by others) up to 1997, and the collecting season was from late May to around Midsummer. However, for comparison purposes it is interesting that it is in the nesting period, as are the observations of Linda and Sulev. Ekblad notes that the pellet remains are probably mostly from the young, but that there is no reason to assume that the diet of the adults would be much different.

However we calculate and guess at the proportion of birds vs fish for Linda & Sulev, they seem to be exceptionally kind towards their fellow birds, compared to the average WTE in literature!

EDIT: Yes, Willgohs is in the ref.lists of both Ekblad and Tiit Randla. Ekblad's work is also interesting in that data are from the Baltic. But I don't know how "different" the North sea and the Baltic are from a WTE point of view! Nor how the WTEs see the Åland isles vs the Estonian coast. Renno, Urmas, other eagle specialists - any ideas?

Re: Bird Behavior: A Discussion

Posted: July 14th, 2010, 10:54 pm
by Liis
Food deliveries, rather than feeding occasions, is of course the relevant basis for trying to calculate the proportion of fish and birds in what Linda and Sulev brought to the nest to feed their eaglets.
A quick check: in food deliveries during 7 random days after the eaglets had been hatched (2009; May - 3 days; June - 4 days) , there was still much more fish, 26 fish vs 5 birds, or 84% fish, 16 % bird prey.

In the Åland isles study birds dominated, and fish and birds were at most equal during some years.

Sulev's and Linda's food deliveries varied between 2 and 6 times per day.
Food deliveries were obviously fewer than feedings; food was quite often saved in the nest. It seems that birds were finished off at once, but it may be difficult to distinguish saved bits of bird and of fish.

All still according to posts and screencaps.

If I were a bird parent, I would definitely prefer fish. It must be so much easier to serve, not having to defeather it. :innocent:
PS. But there are more calories in bird and meat: 8 kJ / g vs 5 kJ / g for fish.

Re: Bird Behavior: A Discussion

Posted: July 20th, 2010, 9:47 pm
by Liis
While we are waiting and hoping for the WTE camera ...
Here is the English abstract to the study by Camilla Ekblad on WTE diet during their nesting period on Åland / Ahvenanmaa. The results have been discussed here as comparison to what Sulev & Linda brought to the nest.
The rest of the text is in Swedish (link HERE). Please ask if you want to know more about something: there are several Swedish-speaking members in the forum.

Åland / Ahvenanmaa is in the Baltic between Sweden and southern Finland, and consists of 6 757 separate islands and isles.
Material from about 66 eagle nests was collected during the 22-year period. 555 visits to nests were made, and 5161 individual remains of prey (fish, birds, mammals, other) were identified.

Nesting time diet of the White-tailed Sea Eagle in different archipelago zones on the Åland Islands
The subject of this study was the diet during the nesting time of the white-tailed sea eagle Haliaeetus albicilla in different archipelago zones on the Åland islands during the time-period 1978-1999.
The aim was to investigate whether the diet of the sea eagles differs according to the archipelago zone where they breed, if the diet of closely nesting eagles differs, and if the diet of the sea-eagles on Åland has changed during the time-period 1978-1999.
The material of the study was prey remains that annually were collected under the nests by surveyors of the WWF sea-eagle working group. Every piece of prey found was collected and identified by experts. I was allowed to use this material in my study.

Åland was divided into four archipelago zones; inner main Åland (FÅI), outer main Åland (FÅY), middle archipelago (M) and outer archipelago (Y). The territories of the eagles were cathegorized by a confidential map shoving the territories of the sea-eagles on Åland. At first the proportions of the main prey groups; birds, fishes and mammals were compared at different archipelago zones. Thereafter the prey species of birds and fishes were cathegorisized according to if they occur in the inner, outer or over the whole archipelago. Then it was measured in what extension eagles nesting in different archipelago zones fed on the different types of prey species. The preferences of single eagle pairs and differences in single prey species was also investigated. To avoid old prey remains in the year analysis only remains collected at nests with successful nesting were used here. It was measured whether the distribution between birds, fishes and mammals had changed during the period 1978-1999 in different zones and on the whole Åland, and if the distribution of single prey species had changed during the same period.

A total of 84 different prey species were encountered, of which 22 added up to at least 1 % of the total amount (n =.5161). More than 90 % of the prey remains were birds and fishes. The main prey was birds in all zones except in inner main Åland (on average 66,2 %), thereafter fish (28,5 %), and least mammals and other preys (5,3 %). The main prey group in inner main Åland was fish. The most common single prey was eider (Somateria mollissima) and the second most common pike (Esox lucius) in all zones except inner main Åland, were pike was most common, followed by bream (Abramis brama) and eider.

The species composition of birds preyed upon differed between the archipelago zones. The eagles nesting in the outer archipelago and on outer main Åland took more birds that occur in the outer archipelago than did the eagles nesting on inner main Åland. These took more birds that occur in the inner archipelago than eagles nesting elsewhere. Prey birds that occur over the whole archipelago were taken in equal amounts of all eagles. There was no difference between different fish prey types in the archipelago zones. However there was differences between some single fish species. To some account there was even differences within the zones, so that some species were more commonly eaten in some parts of Åland, and others in other parts. Some eagle pairs seemed to have specialized to catch distinct prey species. According to how great a proportion of different prey species the eagles caught, they seemed to prefer mergansers (Mergus sp.) if these were accessible.
The diet of the eagles changed during the period 1978-1999. The proportion of birds increased over all, in the middle archipelago the bird proportion increased and the proportion of fish decreased, and in the outer archipelago the proportion fish decreased. Eider increased in the whole material, while great crested grebe (Podiceps cristatus) and pike decreased. The proportion of pike decreased because the pike had decreased especially around Föglö, but also on the rest of Åland. The decrease in great crested grebe seems to derive from the fact that the prey remains in the beginning of the research period emanated from only a few territories, of which two had specialized to hunt grebes. The proportion of eiders probably increased to compensate the loss of pike. The proportion of fish decreased because the proportion of pike decreased. The proportion of other fishes did not decrease.

The results indicate that the eagles prefereably took prey that was accessible in the neighbourhood of the nesting territory, and that the prey varied between the zones due to unequal accessibility.
Sometimes the eagles hunted further from the nesting territory. In general the eagles took more birds and less fishes the further out in the archipelago they nested. The diet of some eagle pairs differed from their neighbours, partly due to the availability of prey species but also because some eagles had specialized in hunting a particular prey. The prey preferences of single pairs was overrated during years with less material. The population fluctuations of important prey species was visible in the prey material. If an important prey species decreased it was compensated by an increase in the most accessible prey. Changes in pike remains could be used as an indicator for the state of the pike populations.

(Author's abstract)

Re: Bird Behavior: A Discussion

Posted: August 4th, 2010, 10:11 am
by Liis
WTEs feeding eaglets, another comparison

On June 17, 2002, Urmas (Sellis) :wave: observed a WTE nest at Härjanurme (village in Tartu county, Estonia). During the day the parents brought in
1 pike; 1 cyprinid (carp / minnow family fish); 1 nestling age bird, species unidentified

On June 17, 2009 Linda & Sulev brought to the nest
2 white birds (probably cygnets)

On June 17, 2010 Linda & Sulev brought
3 fish

The observation by Urmas is from an interesting investigation of WTEs and fish losses from carp ponds, full text HERE, printed source Proc. Estonian Acad. Sci. Biol. Ecol., 2007, 56, 3, pp. 209 -223 (in English)
Abstract here:
The impact of the White-tailed Eagle Haliaeetus albicilla and the Osprey Pandion haliaetus on Estonian Common Carp Cyprinus carpio production: How large is the economic loss?
Joosep Tuvi and Ülo Väli
Received 29 March 2006, in revised form 16 May 2006

Protected bird species have been suspected to be a cause of a significant economic loss at Estonian fish farms, but its extent has remained unexplored. We counted the number of White-tailed Eagles and Ospreys, and the quantity of fish they take, and analysed the economic loss in five carp farms in 2001 - 2004. Each of Estonian four larger carp farms was used by a pair of breeding Whitetailed Eagles, and by up to three immature birds, whereas Ospreys were recorded at all five studied farms. The average daily number of foraging White-tailed Eagles per farm was 1.3 - 3.3; the number of birds was constant during the breeding period but differed between years. The average number of Ospreys (0.5 - 2.8) fluctuated both within and between years. White-tailed Eagles foraged upon 300 - 1050 g third-year fish, and caught on average 0.4 fish per day per eagle. Ospreys took third-year fish at the beginning of the breeding season but second-year fish later; they always selected fish weighing 200 - 400 g, and caught 0.3 - 3.7 fish per day. The total amount of fish taken by the two species differed significantly between years and regions. The extent of loss caused to a fish farm depended on the methodology used for estimation. Calculations based on potential final weight of fish were on average 44% higher than those based on current weight, and constituted up to 4% of the total price of fish sold, and 2% of the total weight of fish reared by the company.
Key words: freshwater aquaculture, fish pond, foraging ecology, piscivore, birds of prey, economic loss, damage estimation.

Joosep Tuvi was the eagleman who ringed Spot. One of the observed carp ponds was at Ilmatsalu (Forest/Boar Camera 1 area)
They also say in the text : The diet of the White-tailed Eagle contains mainly fish and waterfowl, with the proportion of fish ranging from one third to four fifths depending on the region, year, and method of analysis (Cramp & Simmons, 1980; Helander, 1983; Randla & Tammur, 1996; Sulkava et al., 1997)

Re: Bird Behavior: A Discussion

Posted: August 5th, 2010, 3:19 am
by alice44
It is interesting that on this day eagle parents brought plenty of food in multiple years -- at least when the eaglets were younger it seems there are days when they are mostly being fed out of the freezer. As they get older and bigger and the weather is warmer I guess there is less of that, but still some days do not seem to include much in the way of food deliveries.

I had forgotten that two cygnets were delivered the same day. I guess when the eagles find a good easy food source they are quick to go back.

Re: Bird Behavior: A Discussion

Posted: August 5th, 2010, 8:59 am
by Liis
alice44 wrote:It is interesting that on this day eagle parents brought plenty of food in multiple years -- at least when the eaglets were younger it seems there are days when they are mostly being fed out of the freezer. As they get older and bigger and the weather is warmer I guess there is less of that, but still some days do not seem to include much in the way of food deliveries.

I had forgotten that two cygnets were delivered the same day. I guess when the eagles find a good easy food source they are quick to go back.
Alice :wave: -
I am not really sure about 1 or 2 birds that day; posts and screencaps were ambiguous, and you have quite certainly looked more carefully.

Various sources* agree that a WTE nestling needs 350 g of fowl or mammal meat, or 600 g fish (not quite sure if that includes inedible parts) per day, and at the end of the nest period up to 500 g fowl or 800 g fish per day. On the other hand Urmas (Renno?) has said that they can easily be without food for a day or two, and that the parents may sometimes even put overfed youngsters on a slimming diet to make fledging easier.
:book: Multiplying the rations by 2, and considering the size of fish brought in, it seems to need a lot of deliveries, and/or a well stocked pantry.
How much does a "huge fish" weigh?
Is really all spare food kept stored in the nest?

* Many sources seem to go back to Björn Helander (Sweden).

Re: Bird Behavior: A Discussion

Posted: January 14th, 2011, 11:24 pm
by Jo UK
Another report about the different uses of tools, by crows. ... 353588.stm

Re: Bird Behavior: A Discussion

Posted: January 15th, 2011, 1:57 am
by alice44
Jo UK wrote:Another report about the different uses of tools, by crows. ... 353588.stm
Very interesting -- I wonder if the crow would have tried a slightly bigger stick on the "spider" if one had been available.

Re: Bird Behavior: A Discussion

Posted: January 21st, 2011, 4:20 am
by alice44
I am listening to a report on the use of white plastic in Black Kite nests in Spain.

This report suggests that it is used as a marker for young strong Kites (but it is just one study so there is some disagreement). I will see if I can find something online. ... 10119.html

NPR story I was listening to -- this one has some nice pictures of the nest and a nice Black Kite image ... s-vitality

Science News -- also has pictures ... als_at_bay

Re: Bird Behavior: A Discussion

Posted: January 21st, 2011, 7:09 pm
by Mew

Re: Bird Behavior: A Discussion

Posted: March 1st, 2011, 3:17 am
by macdoum
:puzzled: Had to login twice in 10 hrs. ?

Here is an intriguing story of a goose who has befriended a man in the USA ... nds-video/
He doesn't want to take her home yet although he lives alone. (CBS newscast tonight)

Re: Bird Behavior: A Discussion

Posted: April 6th, 2011, 11:09 pm
by macdoum

See the 'Wildlife Whisperer'.;

Re: Bird Behavior: A Discussion

Posted: July 13th, 2011, 10:56 pm
by macdoum

Re: Bird Behavior: A Discussion

Posted: September 13th, 2011, 7:26 pm
by macdoum
This is a map of Offshore Windfarms.. :vangry:

A constant danger for the migrating birds. :cry:

Re: Bird Behavior: A Discussion

Posted: September 14th, 2011, 6:39 am
by NancyM
macdoum, thank you for those good links ... windfarms are endangering our most endangered species (whooping cranes in the US)

Re: Bird Behavior: A Discussion

Posted: September 14th, 2011, 5:39 pm
by macdoum
Well,maybe those windfarms can be a help to migrating birds.....rarely in my opinion. This must be the exeption; ... r-a-lover/


Re: Bird Behavior: A Discussion

Posted: September 19th, 2011, 12:14 am
by Katinka
Wind Power Plants (WPP)
...Because of the current actuality of (migrating)birds being endangered by those installations -
I think there is more need to discuss the topic?!

Due to the last few posts I was getting more busy to the theme and have begun to collect more information - as we do have many migration routes here through Germany.

Since the last years the necessarity to substitute the obsolete power production by coal/nuclear power has become more and more clear. So esp. in Germany we saw a great increase of WPP all around the coast line, and following that all over the land. But the bird's endangering topic never was one to take into consideration for the location of WPPs.

I'll post some more thoughts and explorations, as soon as I'll be prepared to transform German knowledge into English words!
So far for today:
WPP are a necessary alternative for renewing power production - and will never exist without conflicts to nature belongings. Don't forget: in the opposite NPP are the most-known but most-ignored danger for mankind.