Print 05/03 May 2003

Notes Northern Gannet thermalling I was crossing Ramsey Island Sound, Pem- 200 m before leaving the thermal, partially brokeshire, on the afternoon of 4th July 2002, closing its wings and departing southwards when I noticed several Great Black-backed (towards Grassholm?) at high speed. Gulls Larus marinus and Herring Gulls L. argen- The surface wind was a light westerly and the tatus soaring in a thermal which was drifting air temperature was 21°C. The air mass was eastwards across the Sound. These birds were unstable, with active thermals and fair-weather circling clockwise about 100 m above the sea cumulus clouds forming over the mainland. surface. An adult Northern Gannet Morus bas- Nelson (1978) mentions gannets using slope sanus approached at a low height from the soaring, dynamic soaring and soaring in north and joined the thermal at low level. The standing waves, while del Hoyo et al. (1992) gannet extended its wings fully and began to refer to gannets dynamic soaring; but neither orbit clockwise on stiff wings. It achieved a rate mention gannets soaring in thermals. of climb in excess of the gulls and soon climbed above them, without any flapping action. The References gannet’s rate of climb was impressive. In fact, it del Hoyo, J., Elliott, A., & Sargatal, J. (eds.) 1992. Handbook of the Birds of the World. Vol. 1. Lynx Edicions, Barcelona. looked remarkably like a modern, high-perfor- Nelson, J. B. 1978. The Gannet. Poyser, Berkhamsted. mance sailplane as it gained height to about John Stewart-Smith Mathry Hill House, Mathry, Pembrokeshire SA62 5HB White Pelican taking Feral Pigeon ‘A wonderful bird is the pelican – its beak can to re-emerge in its pouch still alive, and another hold more than its belly can’. This ditty attempt was made to swallow it. On a number appeared to be true on 7th October 2002 in St of occasions the pelican dunked the pigeon, still James’s Park, London. One of the Park’s White in its pouch, in the lake. Whether this was an Pelicans Pelecanus onocrotalus had caught a attempt to drown it, or to wet the plumage to Feral Pigeon Columba livia and was having make it easier to swallow was not clear. The trouble swallowing it. Several times the pigeon meal took more than ten minutes to consume. seemed to be safely in the pelican’s gullet only BWP mentions only fish as food. Alan Gibson 40 The Avenue, Muswell Hill, London N10 2QL Egg weight and growth of nestling Merlins in Dumfries & Galloway There are few published data on the growth of again three weeks after incubation started; all nestling Merlins Falco columbarius in the wild, the eggs hatched. One brood of four nestlings apart from one study in Orkney (Picozzi 1983), was weighed just after hatching, when the and another, of the race F. c. richardsonii,in young were in the first 24 hours of life and were urban Canada (Sodhi 1992). Between 1971 and therefore of known age. Five other broods were 1977, seven broods comprising a total of 28 first weighed when the young were 1-3 days old nestling Merlins from ground nests were (estimated by backdating, using other nestlings weighed regularly in Galloway, Dumfries & Gal- of known age as a reference), and all young loway. Six of the broods (24 nestlings) survived were weighed at intervals of 6-7 days thereafter. to fledging, but one brood was predated, prob- All were individually marked using coloured ably by an Adder Vipera berus (Shaw 1994). pens until they were ringed. In 1973 and 1974, Eggs were weighed when newly laid, and the outermost (tenth) primary of nine nestlings 252 © British Birds 96 • May 2003 • 252-257 Notes 250 female’s body mass (212 g). A clutch of four eggs would therefore weigh 200 about 88 g on average, or about 42% of the female’s 150 body mass. The heaviest clutch of five fresh eggs in this study was 115 g (54% 100 of the female’s body Mean weight (g) Mean weight mass), while the lightest 50 clutch (of five eggs) was 103 g (49%). The mean 0 weight of 13 eggs incu- 0 5 10 15 20 25 30 bated for three weeks was Age (days) 18.3 g (SD ±0.72), an average loss of 3.7 g per Fig. 1. Mean weights of nestling Merlins Falco columbarius in Galloway, egg during incubation. Dumfries & Galloway, 1971-77 (see also table 1). Nestling weights 300 All the nestlings grew 250 2a.Weight (g). quickly, with mean mass 200 of 13. 7 g (±2.06) at 1-2 150 days old, 72.7 g (±11.4) at 7-8 days old, 184.1 g 100 Weight (g) Weight (+24.0) at 15-16 days old, 50 and 226.8 g (±20.7) at 21- 0 22 days old (table 1, fig. 05101520251). Few nestlings were Age (days) weighed after 23 days, since they are prone to 160 fledge prematurely at this 2b.Wing length 140 age. Two were, however, 120 (WCL – see text). 100 weighed after their first 80 flight, at 25-26 days old; 60 their post-fledging 40 weights were 186 g and Wing length (mm) 20 214 g, within the range of 0 0510152025adult males and females Age (days) respectively. Fig. 2 shows the weight Fig. 2. Weight and wing length of a brood of five nestling Merlins Falco and wing length (WCL) columbarius in Galloway, Dumfries & Galloway, 1973.There is a clear of a brood of five distinction between males and females by the age of 23 days: the three nestlings in 1973. This nestlings with the highest mass and longest wing length are females. indicates that there is a clear distinction between was measured. To derive wing-chord length male and female nestlings at 23 days old, in (WCL), 30 mm was added to the measurement both wing and weight measurements, and sug- of P10 (growing feather plus sheath). Weights of gests that the three chicks with the longest wing adults were taken from BWP. length and highest mass at that age can be sexed accurately as females, while the two with the Egg weight shortest wing and the lowest mass were males. The mean weight of 20 freshly laid eggs was Similar results were obtained in 1974. 22 g (range 20.0-23.5g, SD ±1.09); each egg Craighead & Craighead (1940) considered thus constitutes about 10% of an average that it was possible to sex nestlings by body- British Birds 96 • May 2003 • 252-257 253 Notes Table 1. Mean weights of nestling Merlins Falco columbarius in Galloway, Dumfries & Galloway, 1971-77 (see also fig. 1). Age (days) Sample size Mean weight (g) Range Standard deviation 1-2 6 13.7 11-16 2.1 3-4 11 26.2 19-34 4.7 5-6 7 46.3 37-50 5.6 7-8 6 72.7 57-90 11.4 9-10 11 97.1 81-140 16.9 11-12 3 130.7 127-136 3.9 13-14 7 154.4 135-168 12.8 15-16 9 184.1 139-221 24.1 17-18 8 179.5 165-234 29.8 19-20 5 213.4 203-231 10.8 21-22 9 226.8 187-272 30.7 23-24 4 217.8 189-234 17.3 25-26 4 216.3 186-260 27.2 weight and size of feet at 5-6 days old. The sex using Sodhi’s equation of (WCL + of nestlings in this study could not, however, be 22.482)/8.568. Although this equation was determined by weight alone at an early age. In derived from a population of a different sub- fact, some lighter nestlings gained weight faster species, it would appear that it can be used to to overtake siblings which had been heavier ini- assess the age and sex of nestling Merlins accu- tially. The average mass for males at 17 days was rately in other parts of their range. 180 g in Orkney and 192 g in urban Canada, and for females 230 g and 250 g respectively References (Picozzi 1983; Sodhi 1992). In this study, the Craighead, J. J., & Craighead, F. C. 1940. Nestling Pigeon Hawks. Wilson Bull. 52: 241-248. average mass at 17 days was 193 g for males and Picozzi, N. 1983. Growth and sex of nestling Merlins in 225 g for females, and therefore comparable Orkney. Ibis 125: 377-382. with the results in Orkney and Canada. Conse- Shaw, G. 1994. Merlin chick killed by Adder. Scot. Birds 17: 162. quently, the sex of nestling Merlins in Dumfries Sodhi, N. S. 1992. Growth of nestling Merlins. Canadian & Galloway was estimated fairly accurately Field Naturalist 106: 387-389. R. C. Dickson Lismore, New Luce, Newton Stewart, Dumfries & Galloway DG8 0AJ Pair-hunting by large falcons The recent notes on this topic (Brit. Birds 96: sonally observed a pair of Sakers unsuccessfully 39-43) made no specific mention of Saker hunting the first four prey species on 9th Falcons Falco cherrug, which prompts the fol- October 1997, at the Csaj-tó fishponds in lowing comment. Gorman (1998) described a southeast Hungary. By contrast, the attacks on pair of Sakers hunting co-operatively in the other three species reported by Gorman, in Hungary, and pursuing species including Little different parts of Hungary, were successful. Egret Egretta garzetta,Avocet Recurvirostra avosetta, Spotted Redshank Tringa erythropus, Reference Black-headed Gull Larus ridibundus, Northern Gorman, G. (1998). Saker (Falco cherrug) using a co- Lapwing Vanellus vanellus, Feral Pigeon operative hunting strategy.

Load more