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| Woodcocks http://lbcarchive.co.uk/forum/viewtopic.php?f=3&t=24346 |
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| Author: | Andrew Henderson [ Fri Jun 10, 2016 5:10 pm ] |
| Post subject: | Woodcocks |
I am about two-thirds through my woodcock monitoring visits for 2016 and wondered if others (Stuart, John, ...?) were doing it this year. My results so far suggest an overall decline on the previous surveys in 2003, 2013 & 2014. The north-west part of Lincolnshire has been the least affected in the county by the national decline (see the account in the 2013 LBR) but it seems that even here, they are now on the slide. Yet another specialist woodland bird destined to become a rarity? 2003 Crowle 0.3/1; W Laughton 11.0/14; E Laughton 4.0/4; Stonepit 10.0/12 2013 Crowle 0.3/1; W Laughton 8.7/10; E Laughton 4.3/5; Stonepit 13.3/19 2014 Crowle 0.0/0; W Laughton 11.3/13; E Laughton 6.7/9; Stonepit 8.3/13 2016 Crowle 0.0/0; W Laughton 7.5/8; E Laughton 4.0/5; Stonepit 6.0/6 each set of figures is mean/maximum number of passes by roding birds in 75 minutes at dusk from a fixed point. |
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| Author: | Robert Carr [ Tue Jun 21, 2016 8:40 am ] |
| Post subject: | Re: Woodcocks |
I did the third survey yesterday, north of Ostlers plantation, Kirkby Lane, Woodhall Spa. I've seen two birds together once in 2013; every other visit in every year has been of single birds, flying in varying directions, and I'm at a complete loss to understand how this is interpreted by BTO. One bird flies east then a bird flies west on the same track 3 minutes later. Is this one bird which doubles back or a different bird? What about the occasional sighting of a bird flying south in the same area? What about birds flying on a different track, c100m south of the usual track? I'm also not sure how the mean is calculated - number of sightings divided by ? Rob |
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| Author: | Andrew Henderson [ Tue Jun 21, 2016 10:47 am ] |
| Post subject: | Re: Woodcocks |
My quoted means were simply the averages of the visit counts; thus with 6, 6 and 5 passes, the mean is 5.7. One cannot be certain of the actual number of individual roding males at a single site (without sonographic evidence) but GWCT research has demonstrated a general correlation between the numbers of passes (in whatever direction) at sites and the numbers of roding males. As with other extensive surveys, such as BBS, the results from an individual site are fairly meaningless but credible trends can be calculated from numerous sites covered using a standard methodology. There's quite a bit on estimating woodcock numbers in the literature, including http://onlinelibrary.wiley.com/doi/10.1 ... x/abstract which is freely available as an abstract but you'll need an Ibis subscription to read in full. Essentially, it's likely that anything under four passes in an hour (or 75 minutes) is likely to relate to one male only (or possibly two). Twelve or more passes may mean five or more males. and also, freely available http://www.bto.org/sites/default/files/ ... odless.pdf which discusses the results of the 2003 survey. General information on the woodcock survey (and more links) are at http://www.bto.org/volunteer-surveys/woodcock-survey Some of the sightings of more than one together may involve male(s) + female. The most I've seen at one time in these surveys was four, and I had the distinct impression that it was three males chasing one female (a la mallard). |
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| Author: | Robert Carr [ Wed Jun 22, 2016 12:29 pm ] |
| Post subject: | Re: Woodcocks |
The papers were very interesting - using analysis of recorded calls to identify males. For what it's worth, my results are: 2013 6.3/9 2014 5.5/7 2016 8.0/10 An obvious increase! Rob |
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