A request from Jeroen Reneerkens….

Dear Sanderling observer,

Early July, I have told you about the poor breeding success of Sanderlings in Greenland and asked for your help to count adult and juvenile Sanderlings in the flocks you observe. It is late August now and that is the time that you can usually observe most juvenile Sanderlings. Therefore, I would like to remind you of my earlier request and kindly ask again for your help. I very much would like to document whether the extensive snowpack in Greenland this year has affected the population’s reproductive success, and to which extent. Because the number of juvenile Sanderlings varies considerably with date and location, I can only document this if many of you are willing to help.

I have already received many useful counts and I like to thank everyone who has already participated so far. But the coming two months will be the most essential to make a good comparison with earlier years, so I hope to receive even more information from you.

What is needed:

Some reports were –despite without doubt good intentions – however not as useful, so I take this opportunity to explain how the counts preferably should be done to avoid disappointment for both of us.

We need three pieces of information for each count: (1) the number of individually counted juveniles, (2) the number of individually counted adults and (3) the total (counted or estimated) flock size.

It is of course impossible to individually determine the age of each individual when you observe a flock of 3,000 Sanderlings. Therefore, I would like to ask you to determine the age of as many as possible individuals within such a large flock and let me know the above three numbers. If a flock consists of 30 individuals only, then of course it will be much easier to age and precisely count each individual.

Next to that I also would need the date and location (preferably including coordinates), and your name.

Often made mistakes:

I receive e-mails with the following information:

200+ Sanderling, almost all were adults.

I saw 3 juveniles in a flock of ca. 500.

I counted the first 6 juveniles today.

Unfortunately, I cannot use this information because it is not precise enough. The birds you age need to be counted one by one and I need to know how many adults and juveniles you counted, also when the flock consisted of adults (or juveniles) only. The total flock size may be estimated (but please try to estimate it as precisely as possible).

Also, some observers send me photos of flocks. Unfortunately, this is not useful either, because –even if I can age every individual on the photos- I do not know how big the total flock was, and whether or not some individuals appear on more than one photo.

How to report?

You can send the information by e-mail to J.W.H.Reneerkens@rug.nl

Thank you very much! I look forward receiving your reports, and truly hope that we will see more juvenile Sanderlings than expected based on this summer’s conditions in Greenland!

Jeroen Reneerkens

PS Some background news about the poor breeding season can be found here:




All photos copyright Jeroen Reneerkens.