Let's continue this week to explore the different scientific questions of the ADACLIM program... and discover what the main lessons of this long-term monitoring are...
Question #4: Where do little auks spend the winter?
To answer this question, around thirty birds are equipped each year with a light sensor (GLS), which makes it possible to determine (with relative precision) their longitude and latitude.
bird equipped with a GLS, fixed on a pierced metal ring on the right leg, and a green ring on the left leg (to facilitate its observation)
But to recover this precious data, we still have to... recapture the birds the following summer!
To do this, I'm going to give you some tricks: arm yourself with a piece of string, some patafix, and a lot of patience (if you have a few days ahead of you, it's better 😉), make a lasso, which you will place on the bird's favorite stone, wait for it to put a paw through the loop... and... PULL!
map of the wintering areas of different little auk colonies; for the colony studied in East Greenland "EG" this is the pink zone off the coast of Newfoundland (Fort & al, 2013), where winter storms are common
Question #5: What is the diet of the little auks? and what do they bring back to their chick?
This time, locate an adult whose gular pouch, under the beak, is very swollen (or even dripping with fat) then capture it, and empty it for him (sorry old man, it's for Science). Then weigh the samples in the laboratory and determine the prey species.
little auk with a swollen gular pouch, from which protrudes an unusually large prey (Themisto libellula), while the vast majority of its prey are small copepods a few millimeters long (see below)
The main observation from the analysis of these diets is that the different species of copepods on which the little auk feeds move northwards. With a major problem: the southernmost species is less rich in lipids than the other two, and therefore less interesting in energy terms for feeding the chick.
Question #6: Where do adults go to feed? how many dives do they do? how much energy do they expend?
Method: capture a breeding adult, attach a small marvel of ultra-light technology (GPS or time depth recorder or accelerometer) to the feathers using special tape, make a colored mark on it at the level of the chest (to then spot it more easily), then let it go about its business for 3 to 4 days.
And then... try to recapture it! to remove the device from it and be able to unload the data.
bird equipped with a time depth recorder (2015)
Here are some figures from the analysis of the data collected by these devices:
- the little auk feeding area is located about 100 km off Kap Høegh
- the average duration of a complete trip is 32 hours
- the duration of each dive is approximately 1 minute
- little auks generally dive to depths of 10 to 40 meters!
And the diving profiles can be related to the diet of the little auks, as in the example below:
on the left a "classic" individual, which fed on copepods (white line = 1 mm) at depths of 15-20 m (with around forty dives carried out in one hour !), and on the right a bird which mainly went to feed at shallow depth (<5m) on a species of amphipod associated with sea ice (source: ADACLIM report 2015)
What are the main lessons from this long-term monitoring?
Scientific monitoring has shown that the colony is subject to rapid variation in its environmental conditions, notably with an increase in temperatures and a reduction in the extent of sea ice in summer. These changes are accompanied by a rise in prey species towards the North. Under these conditions, the little auks demonstrate "plasticity" and the colonies of East Greenland could even temporarily benefit from these milder climatic conditions. But the situation is more worrying for the colonies of Svalbard (where the temperature of the marine waters is higher) as well as the threats linked to pollution (mercury, micro-plastics) and the development of new human activities (exploration areas for hydrocarbons, new maritime transport routes) are sources of significant concern and justify the need to continue these studies in the long term.
map of projected future human activities (hydrocarbons in black, maritime routes) with regard to the zones of presence of the little auks in the different seasons, in other words their vital range (Fort & al, 2013)
To know more :
Fort & al, 2013 : Multicolony tracking reveals potential threats to little auks wintering in the North Atlantic from marine pollution and shrinking sea ice cover - Fort - 2013 - Diversity and Distributions - Wiley Online Library
[next episode #5/10] Hut life