194 



KNOWLEDGE. 



May, 1011. 



BIRDS IN LONDON AND THEREABOUTS.— Mr. A. 

 Holte Macpherson contributes his welcome annual " Notes on 

 London Birds" tlQlOt to Tlic Sclbonie Magazine for April 

 (pages 96-971. These notes have now continued for twenty- 

 one years without a break, and are of much value as giving 

 personal observations, mostly in the West-end parks. The 

 literature of London birds is an extensive one. but it is to be 

 hoped that Mr. Macpherson may be induced to publish a 

 review or survey of his obser\ations in a more permanent 

 form. Instructive comparisons would not be a-wanting in it. 

 In the course of 1910, a great crested grebe was seen on the 

 Serpentine on 29th January, and another on the Round Fond. 

 Kensington Gardens, on 11th July. Mr. Macpherson had only 

 once seen this fine species in London previously, and points 

 out that it is remarkable how it has increased near that city 

 during the last few years. Virginia Water and Richmond 

 Park are nam«d as haunts of the bird, to which we would add 

 Ruislip Reservoir. Greater London holds within its area the 

 " Brent Valley Bird Sanctuary," an account of which is pub- 

 lished in a small work under this title by Mr. Wilfred Mark 

 Webb. Honorary Secretary of the Selborne Society, of which 

 a third and revised edition, profusely illustrated, has just been 

 issued (The Selborne Society, 42, Bloomsbury Square, London. 

 W.C., 34 pages, price 6d., or in paper boards, !■), The 

 Sanctuary has been maintained now for about six years with 

 results which redound to the praise of the Committee who so 

 vigilantly look after it, and are gratifying to all who care for 

 our native birds. Nesting boxes, made on the spot, have 

 been used since 190S as a method of attracting birds and 

 have proved iiuite successful, being largely used. Within this 

 limited area of nineteen acres, possessing no outstanding 

 natural advantages, thirty-six species (almost entirely smaller 

 woodland birds) have now nested, and eighty-six species in 

 all, including occasional visitors, have been observed in or 

 close to the place. 



A MIGRATION "RUSH."— The Irish newspapers report 

 that a migratory movement of an extended character was 

 observed on 29th-31st March, conspicuously in South-east 

 Ireland. The weather conditions were still and dark, the 

 moon being in her dark phase, and at the same time fog 

 prevailed. These conditions are conducive to migrants 

 showing themselves. The migrating flights seem to have 

 been attracted by the lights of the towns, just as they often 

 are by lighthouses. In New Ross a swarm of starlings 

 descended on the town about ten o'clock and the streets 

 were littered with them. House-windows were broken and 

 numbers of birds entered the houses. In Kilkenny many 

 hundreds of birds fell dead in the market-place and else- 

 where. In Carlow the destruction which befel the birds is 

 said to have been caused by them coming into contact with 

 telegraph and other wires. Immense flocks of Curlew passed 

 over this town on the night of 29th March, in a N.E. direction, 

 being recognised by their shrill whistling. 



The other kinds of birds named in the reports are thrushes, 

 blackbirds, redwings, and sparrows, but, no doubt, many 

 species were unrecognised. Amongst them probably occurred 

 some of our first summer visitants for this season. 



CROSSBILLS IN THE BRITISH ISLES.— An account 

 of the irruption of crossbills which took place in 1909, is given 

 in the April number of British Birds (Vol. IV. pages 326-331). 

 First observed at Fair Isle, on 23rd June. 1909, the arrivals 

 continued until about 10th August. The birds appeared 

 rather later in southern districts than in the north, and by the 

 latter part of July their numbers were decreasing in Scotland. 

 In England they were much in evidence during July and 

 increased until well into August. During the winter they 

 were recorded from all the English counties except 

 Cumberland, Notts, Huntingdon, Cambridge, Dorset, Devon 

 and Cornuall ; and in Wales from Denbigh, Merioneth, 

 Montgomery and Brecon. It is remarked that records are far 

 more numerous from the country lying to the south and east 

 of a line drawn from the Wash to Portland Bill, the sandv 

 soils occurring therein being much planted with pine trees. 

 These trees pro%ide natural food supply for the birds. 



Nesting was recorded as early as 12th January. 1910, near 

 Thetford, Norfolk (three nestlings), and the latest records are 

 25th May, from Sussex and Kent. .All the nests known were 

 in Scots pine, except two in spruce and two in larch. Only a 

 small proportion of the visitants nested, the following counties 

 yielding records, viz: — Kent. Sussex, Surrey. Hants, Berks, 

 Essex (two), Suffolk, Norfolk, Somerset (one), Gloucester, and 

 Stafts (one), also probably Lincoln and Bedford. 



The departure of the birds began in the winter of 1909-10, 

 and this movement was at its maximum from February to 

 June, with a few records for later dates. The visitation thus 

 extended over a period of rather more than twelve months. 



It should be added that the bird spoken of is now designated 

 by modern ornithologists as I.o.xia ciirvi rostra ciirvirostra 

 — the Common Crossbill. 



Mr. H. F. Witherby follows the paper above summari/:ed by 

 an article (pp. 332-334) on its status as a British bird, of which 

 the following is an abbreviated summarj', viz.: — 



England and Wales. — An early autumn inunigrant 

 (mid-June to August), irregular in most districts. Periodically 

 (every three to ten years) arrives in great numbers, and 

 becomes much more generally distributed, frequenth' staying 

 over the following spring and into summer. .Authentic records 

 of nesting are so few and far between that the bird cannot be 

 classed as a resident, but only as a migrant, breeding 

 sporadically (nesting counties are named by Mr. Witherby). 

 Crossbills have been found this spring (1911) to be breeding in 

 localities in which they bred last year, the first time they are 

 known to have nested in two successive years in the same 

 district. 



Scotland. — Immigrant as in England, but not so regular. 

 Breeds sporadically and rarely in Southern Scotland (counties 

 named). 



Ireland. — Now resident but not indigenous. Apparently 

 only migrates to Ireland in years of " irruptions." Following 

 that of 1SS7-S became established as a breeding bird. 



The Scottish Crossbill, Loxia ciirvirostra scotica Hart, 

 which is confined as a breeding bird to Scotland, is 

 resident in Northern Scotland, where it breeds in certain 

 localities (named). Has occurred sporadically in winter in 

 \ery small numbers in Southern Scotland (counties named). 



PHOTOGRArHY. 



By C. E. Kenneth Mees, D.Sc, F.C.S., F.R.P.S. 



THE MEASUREMENT OF S U R F ACE 

 BRIGHTNESS. — Under this title a paper was read at the 

 Royal Photographic Society, on March 28th, 1911, by 

 Messrs. J. S. Dow and V. H. Mackinney, describing a small 

 portable photometer under the name of the " Holophane 

 Lumeter." which is intended for the measurement of the 

 intensity of the light reflected from various objects. 



In the instrument, the surface whose brightness is to be 

 measured is observed through an aperture in a white opaque 

 surface, the discs surrounding the aperture being illuminated 

 by means of an opal glass behind which is an Osram lamp, 

 run off an accumulator. The area of the opal glass can be 

 restricted to any required extent by means of black sectors, 

 and the intensity of the illumination read to one per cent, by 

 means of scales, the maximum opening representing an 

 intensity of one foot candle. 



The accuracy claimed for the instrument is about five per 

 cent., which will clearly be sufficient for most practical 

 purposes. 



By means of two supplementary black glasses the light 

 from the external surface can be cut down to one-tenth or 

 one-hundredth of its original amount, and the maximum 

 intensity measurable can thus be made ten or one hundred 

 foot candles. 



This range seems to me insufficient, and it would probablv 

 be better to add other densities to extend the scale to one 

 thousand and ten thousand foot candles. 



