Some interesting eider figures....

Nate Grace

Nate Grace

Well-known member
I am doing some research for a book that I hope to publish on eider ducks, and came across some interesting, if not fairly shocking, information about eider chick survival and predation of chicks by black-backed gulls in the Bay of Fundy.

Check this out - from seaducks.org:


Status of the common eider (Somateria mollissima) in New Brunswick.
MAWHINNEY, KIM. Atlantic Cooperative Wildlife Ecology Research Network, University of New Brunswick, Fredericton, New Brunswick E3B 6E1
DIAMOND, A.W. Atlantic Cooperative Wildlife Ecology Research Network, University of New Brunswick, Fredericton, New Brunswick E3B 6E1

In 1995 we conducted a pilot study of brood ecology of the Common Eider Somateria mollissima with specific reference to movements, habitat use and behaviour of both adult females and ducklings on the Wolves Archipelago in the Bay of Fundy. Information generated from this colony, particularly recruitment, over the next 3 years was to be used in conjunction with information collected from other breeding colonies to develop a model of the role of post-hatch ecology in the demographics of Common Eiders in the Bay of Fundy. Exceptionally high depredation rates by Great Black-backed Gulls Larus marinus on Eider ducklings precluded the study of brood amalgamation as only 12 of 3000 ducklings produced in this colony fledged. In 1996 breeding pairs of Great Black-backed Gulls were eliminated on two of the five islands in the Archipelago and clutches were prevented from hatching on two other islands. Great Black-backed Gulls on clutches that were oiled to prevent hatch had a protracted incubation period, and the absence of chicks did not reduce adult Great Black-backed Gull depredation on Eider broods as only 8 ducklings fledged.Duckling mortality on the Wolves Archipelago exceeded 95% in both 1995 and 1996. Brood surveys suggested that low duckling production was not confined to the Wolves Archipelago; and that duckling production in the Bay of Fundy has declined considerably over the last decade despite stable numbers in breeding pairs. High duckling mortality is a common phenomenon in Eiders and survival of ducklings does not apparently regulate Common Eider population numbers; however, it may potentially limit the growth rate of the population. Although the numbers of Common Eiders breeding in New Brunswick appear stable, we cannot be complacent; low annual recruitment over periods of several years has been associated with gradual declines in breeding populations of Common Eiders elsewhere.


Very best,
Nate Grace
 
Thanks, Nate. That was most interesting. Glad you took the time to post it. It is amazing that this specie is still around. Reminded me of baby sea turtles when born during the daylight hours. The Frigate birds can wipe them out with ease before they reach the water.
Al
 
Wow, 95% mortality is stunning. Few species can stand that lack of success for any period of time. Eiders are my favorite sea duck, favorite duck overall except for woodies in a beaver swamp. Is there additional research available about the trends for the species?
 
Nate - Thanks for posting. I would be surprised if our eider numbers are not also down due to hunting pressure. I say this because of the increase in sea duck hunting and guided sea duck trips on the N E coast - coupled with the bird's tendency to decoy readily. I have missed decoying eider ducks and then had them circle and come back in for round 2. With less available public access everywhere in New England, I think it has put more pressure out there on the sea ducks. I had no idea that they could have such a poor survival rate for young of the year and I wonder if this is something localized to the study area or true in general ?
Hopefully our seasons and bag limits will insure that we do not put more pressure on eiders than they can stand. They are certainly one of our finest waterfowl and sea ducking has been a grand tradition for generations. Eiders need to be around for generations to come.
Thanks again for posting this !
sarge
 
Dick,

I have a feeling that the numbers have continued to trend down since these numbers were first released. I am reading another study that was done by the Maine Dept. of Inland Fisheries, and in it they discuss some research that was done in New Brunswick from 1995 to 1998 where they found that 100% of eider ducklings hatched were consumed by black-backed gulls. Hunting pressure is another factor. In 1960 there were 1,100 eider killed in Maine, 200 in Mass., and 100 killed in other states. Compare that with 1999 when this study was completed, 16,000 eiders were harvested in Maine, 4,300 in Mass., and 2,500 in other states. I would suspect that those numbers have increased significantly in the last 10 years.

One paragraph in this study about Population Projections really stands out:

Although the numbers of eiders breeding and wintering in Maine appear high, the status of those populations could change rapidly. Common eiders have low recruitment and high adult survival rates thus there is concern that continued increases in harvest rates, combined with natural mortalities (avian cholera and high predation rates of ducklings by a burgeoning Great Black-backed Gull population) could result in a dramatic decline in eider numbers. More information on population abundance, survival rates, recruitment, and harvests, and other potential limiting factors is needed in order to make reliable eider population projections.


Very best,
Nate Grace
 
John,
I am seeing fewer cormorants on the ohio river this year,maybe the steps taken by the dnr on the islands is starting to work i hope.
Bill.
 
Cormmerants are one of the great success stories...much like the Wood duck. I wonder how happy every one is about that!?

I am sure the reason that there is not a season is wanton waste (however you spell that)... How many people would actually eat either of those birds? I wish we could shoot gulls....
 
so i have a question for ya why cant we shoot seagulls ???whats the reason whats the science ???etc..why isnt there culls on them.. like the corromant...
 
If wanton waste is the issue, why can we shoot crows? I've never tried literally eating crow, done it a number of times figuratively.

If they allowed shooting gulls and cormorants, would there be enough pressure to make a difference? I'd be willing to do my share...
 
Wow, that is some pretty amazing information.

Gulls and cormarants.....

A couple years ago they shut down the netting of river hearing here in RI. Guys would go to the streams and rivers and net some for bait for stripers. Well they stopped that, however, any fish ladder int he state will have 100+ cormarants sitting there sucking down the same fish by the 100's.

Guess it's just hard to find a balance in the crazy world of nature.

Thanks for sharing the info.
 
I read a while back that one of the problems with the scaup population was predation
from gulls as they moved inland to the boreal region. I havn't read any more about it
but I've seen what they can do to a duck that is not retrieved quickly. when I was
younger and didn't have dogs I would allow dead birds to drift to shore when the
conditions were right. Had to stop when the gulls started taking them!
They talk about nusance geese but the gulls are far worse!!
John
 
just for you guys ill shoot ya some vid of our crow problem some evening they roost here at work by the thousands
 
Nate are those official numbers from 1960? I ask because back then just between my dad, uncle and their friends they easily shot that many eiders amongst themselves. Your point is well taken though. Back then there was WAY less sea duck hunting pressure for a variety of reasons. In Gillelans' book "gunning for sea ducks" he writes (in the 1980's) that as regular duck hunting continues to decline more and more hunters will take up sea duck hunting. That was 25 years ago.

Good luck with your book.
 
Here is an interesting anecdotal story about gulls and waterfowl..

I will not use names as the person of interest is still alive although retired.

California gulls nest around the Great Salt Lake in considerable numbers and do prey on duck nest and ducklings. A state waterfowl refuge had/has dikes where the gulls would nest....aforesaid person of interest would do dike "repair" every year during the gull nesting season with a D6 cat....of course he wore a hard hat to prevent a bit of whitewashing.

For some reason I do no think that the powers that be, approved of gull nest smashing while doing dike "repairs".....



Matt
 
Matt's story raises the question of whether the underlying problem was gull predation suppressing waterfowl numbers, or habitat modifications (the dikes) creating habitat conditions that allowed gulls to nest in close proximity to breeding waterfowl.

While there are certainly times and places where, for a variety of reasons, losses to predation can be significant, in the long run I don't think they are nearly as important as habitat.
 
Jeff raises an interesting question.. My reply: The Great Salt Lake ecosystem has been extensively modified and include the following: building of the railroad causeway, mineral extraction (evaporation ponds), manipulation of fresh water marshes for waterfowl production, increased gull food sources e.g. dumps. I do not know if gull populations have tended to increase or decrease during the period of 1847 (approximate date of settlement) through the present due to the alterations (fluctuated I am sure). So choose your poison when deciding how to manage predator- prey interactions and populations as the supporting "habitat" has been, and will continue to be extensively modified. I personally would err towards intensive management for waterfowl production but that is my personally bias.

Matt
 
Matt, I almost added a discussion of how, as habitat gets more and more modified and compromised, predator control may become more important because waterfowl population gets concentrated into less and less space, and therefore the juveniles become more susceptible to predation.

Some "fishy" examples--seal predation on salmon at the base of fishways on West Coast rivers; cormorant predation on salmon smolts in the forebays of hydropower dams on rivers out here.

For eiders, though, I don't think this is a factor. Because of where they breed, there hasn't been a whole lot of modification of their habitat, so the predatory issues are probably not related to habitat degradation. On the other hand, I believe that black backed gulls have become far more numerous along the coast in New England and the Maritimes.

These interactions can be complex, the there is always the law of unintended consequences. A bird biologist I know believes there have been substantial declines in nesting success for great blue heron in some rookeries as bald eagle populations on the Maine coast have recovered. Cormorant predation on salmon smolts might not be a major factor if other more abundant bait is available to serve as their primary forage, but if alewife and blueback herring populations (which are swimming upstream to spawn just as Atlantic salmon smolts are migrating out to sea) crash, salmon smolts may be the only vulnerable prey left in the river, and all of a sudden cormorant predation can become a big deal.

It's also important to keep in mind that high juvenile mortality may be normal, and that increases in juvenile survival may not translate into a larger population of adults. If, for example, availability of winter habitat is a limiting factor that controls the population of a species, producing more juveniles to migrate to that limited habitat might even decrease survival to adulthood.

Sorry for the long-winded Sunday night philosophizing. My season has closed, and I have too much time on my hands . . . . .
 
[font=Verdana,Arial,Helvetica]"My season has closed, and I have too much time on my hands . . . ."

Jeff be careful with the "time" on your hands, you might have to get another boat build or??
[/font]
 
You must log in or register to reply here.
Back
Top