Re: Soft-plumaged petrel counts off Port Fairy

[Peter Lansley <>]

Hi all,

thanks for clarifying that Rohan. I agree with most of what you say, however my basic point stands, that is frequently, estimated counts of birds reported on day pelagics off Australia are exaggerated and yes, we can still only say there were definitely five (5) birds (SPPEs) present (and incidentally I think that 72 Shy Albatrosses [cauta] is also a tad optimistic in its accuracy). I should add that I agree that four (4) Sooty Albatrosses were definitely present on the day, since they all had differing plumages. I guess I place less emphasis on birds "apparently showing little interest in the boat when they fly straight past" and consider these as more likely to re-appear, than some other observers. An example from the archives - the South Polar Skua seen on 21 Feb. 1999 off Portland initially reported as 2 birds on boat and I think, the trip report - turned out to be the same bird when the photographs were processed. It disappeared then reappeared later in the trip after an absence of, I think, 15-20 minutes. It should be remembered that when moving between berley stops, flying birds have a better view of the boat than observers have of the birds, and birds can readily track a boat already known to be berleying, from a long distance away - several miles would not be unusual. On a recent Antarctic trip I noted that Soft-plumaged Petrels frequently followed our ship for long period (hours at a time), hence care had to be taken not to double-count. So I think people interested in comparing counts of seabirds at sea should quote only the conservative figure (as Rohan said, the one usually given in brackets in reports on birding-aus) - that is to say, the maximum number we can say were definitely present, whether seen together or otherwise known to be different individuals by way of plumage, moult or markings etc.

Cheerio. Peter.

Rohan Clarke <> wrote:

Hi all, I appreciate Pete's comments. Counting birds at sea is always going to be difficult. This is especially the case where birds are attracted to the vessel with berley over extended periods. On Sunday we berleyed for several hours at three different points that were each 5 to 6 Nmiles apart. As with most seabird reports in Australia the counts I presented are the observer's best estimate (in this case mine) of the total number of birds observed over the day followed by the maximum number of birds seen at any-one-time in brackets. As we saw a bird with a distinctive plumage (a dark morph bird) I also added that within the brackets as it clearly represented a DEFINITE fifth individual.

 

My main reason for suggesting the total count for the day was around 10 (an unprecedented number in eastern Australia) was that we actually had 2 different birds with distinctive plumages. A single dark morph bird and another more typical bird but with pale flashes to the centre of the underwing (that was one of the four birds counted at one time). Both these birds showed little interest in the boat and berley and were each seen, at least by myself, only once . Given the only two birds I could identify as individuals effectively flew straight past without stopping I assume there was also some turn over in typical individuals that I couldn't separate. My counts for the day were;

 

1st berley point: definitely 3 together with 2 almost continuously

Transit to second berley point: 1 following and 1 distant

2nd berley point: definitely 4 together (inc pale winged bird) but 2-3 birds present the entire time.

Transit to third berley point: 2 following and 1 distant

3rd berley point: definitely 2 together plus a 3rd (the dark morph) bird as we departed.

 

My ESTIMATE of 10 for the entire day may be too high as Pete has suggested however if all birds showed as little interest in the boat as the two distinctive birds did (will concede some where clearly more interested) then it may be too low! :) I'll stand by my estimate of 10 but bottom line is Pete, me and everyone else on the boat on Sunday will never know exactly how many soft-plumaged petrels attended. Regardless it was a highlight of the day.

 

Cheers

Rohan

---

Yahoo! Mobile
- Check & compose your email via SMS on your Telstra or Vodafone mobile.