wgeoff

Although this is obviously a good early spring for gulls in general, this has happened before, in particular for Black-tailed Gull which is probably the most significant 'variable peak count' species.

Black-tailed Gull is a regular early spring migrant in southern and eastern waters as well as winter visitor to Deep Bay, but the numbers reported are usually below 50. However, in some years they can be reported in hundreds, as this chart of peak counts by year from 1980 to 2012 shows



Heuglin's Gull tends to be more consistent, although this may be because most Heuglin's high counts are as winter visitors to Deep Bay rather than spring passage migrants to more remote areas as most Black-tailed Gull high counts are.



So I'm not sure this is a recent phenomenon or just another good year for Black-tailed and Heuglin's.

[ Last edited by wgeoff at 11/03/2014 14:35 ]

wgeoff

Yes Mike, it's possible for Black-tailed Gull - all the peak counts are away from Deep Bay.

Avifauna states the peak counts for Black-tailed Gull in years 1975, 1976 (before my graph but given as Fig 191, page 261 in Avifauna) and 1985 were in Tolo Harbour/Starling Inlet. The peak count in 2003 was at Sham Chung and in 2012 was at Po Toi. All were in the February/March period except 70 at Tai Po in January 1976.

Black-tailed Gull is a much more widespread coastal species in early spring (and some peak counts may go unrecorded because they occur in locations that are not well-watched areas).
It's much more difficult to strip Deep Bay out of Heuglin's Gull, but I think almost all the peak counts for Heuglin's Gull were in Deep Bay at various times during the winter.

Later - I can confirm that the four highest counts for Heuglin's Gull since 1999, in years 2000, 2002, 2009 and 2010 (see the graph above) were all in Deep Bay, two in January and one each in February and early March.

Geoff

[ Last edited by wgeoff at 12/03/2014 08:23 ]