414 



NATURE 



[August 31, 1893 



Bird's Steering Methods. 



Mr. Headley's suggestion (Nature for July 27) that gulls 

 sometimes steer by dropping one foot, is, it seems to me, hardly 

 tenable, for so small a rudder acting on so thin a medium as air 

 would be of little effect. And although I have seen many gulls 

 under very varying circumslance-, I have never seen them even 

 appearing to direct their course in such a manner. 



That birds, to a great extent, steer by changing the position 

 of their centre of gravity is undoubtedly correct, and it is espe- 

 cially true of birds with long narrow wings, such as the petrels 

 and sheervvaters. The albatross exhibits this method to per- 

 fection, and anyone who has watched this bird circling far and 

 wide, will have noticed what an angle the outstretched, almost 

 motionless, wings make with the level of the water, an angle fre- 

 quently as great as 45° 



The flexion of the body is, I take it, of comparative little help, 

 difference in force or direction of wing stroke being the main 

 method by which birds direct their course. 



The wings may act synchronously, a change in the direction 

 of one wing causing it to act with more or less force than the 

 other, while such change might be so slight as to elude the eye, 

 or even a camera. A humming-bird will hover about a cluster 

 of blossoms, now hanging motionless, now circling right or 

 left around the flowers, and as there is no turn of the head or 

 swaying of the body, it is evident that the directed force lies in 

 the wings, although their presence is indicated by a mere hazy 

 blur. The body is usually held at an angle of from 30° to 45° 

 with the vertical, and the tail is kept closed, being indeed 

 rarely spread, except when the bird is darting about in the 

 air. 



The use of wings is well shown by the crows, which in fall 

 and winter roost in great numbers on the other side of the Potomac, 

 and may be seen towards sunset winging their way homeward 

 from their feeding places. When the wind is light, the crows 

 fly high and steadily, but in windy weather they may be seen 

 beating back, just skirting the tree-tops, apparently to take ad- 

 vantage of any favouring eddy that may exist near the earth. As 

 the birds dart up and down, and from side to side, one can 

 clearly see the wings open and close, and unless my eyes are 

 very deceptive, the two wings are by no means always opened to 

 the same extent. 



The principal use of a bird's tail seems to be to effect vertical 

 changes in d_irection, and while Hrds with moderately long tails 

 usually have'a more graceful, gliding flight than their abbreviated 

 relatives, they are no more expert on the wing. The flight 

 of the forked-tailed swallow is more pleasing than that of the 

 short-tailed chimney swift, but the swift is quite as much at 

 home in the air as is the swallow. 



Birds with unusually long tails, such as the hornbills, are apt 

 to be but indifferent flyers. 



Washington, D.C., U.S.A., August 14. F. A. LucA.s. 



The Early Spring of 1893. 



The exceptional character of the spring of this year has 

 already been described in these columns. It seems worth the 

 while to inquire to what extent the warm weather commencing 

 in March aflected the limes of flowering of our native flora. 

 The Botanical Section of the Halifax Scientific Society has now 

 for seven years, since 1887, kept a record of all plants observed 

 by its members growing within the limits of the Halifax parish. 

 This, it maybe mentioned, is of considerable extent, perhaps 

 measuring six miles by twelve or more. Thus, the record affords a 

 means of comparing the dates of flowering thi; spring with those 

 of previous years. Of course these will not coincide with records 

 from other districts, as the South of England, but they will 

 satisfy the necessary condition of such an inquiry, viz. that the 

 district should be of limited extent so that the time of flowering 

 of any species in one year is practically the same throughout it. 

 In addition there is the advantage that the draught was not so 

 great ds to retard or kdl the vegetation. On the other hand, 

 such a record must necessarily be open to error; a plant may 

 have been in bloom some time before it was met with ; only a 

 comparatively few species have been recorded iveiy year with- 

 out a break ; some days often intervene between a flower being 

 in bud and in bloom, and the record may possibly, without 

 saying so, refer to the former. However, these errors are partly 

 constant, and may be partly eliminated by neglecting the rarer 

 species, which have only been noted two or three times. 



NO. 1244.. VOL. 48] 



In February almost the only plant to flower was the hazel, 

 seen this year on the 15th, and last year fourteen days later. 



In March twenty different species h ere observed in flower ; of 

 these only half had been previously recorded in March, the other 

 half being equally divided between April and May. Coltsfoot 

 {Tussilago Farfara] and Salix Caprea appeared at the usual 

 time within the first week ; the daisy was not noticed till the 

 31st, whereas it had previously been found on the 29lh ; but 

 almost all the others were very much earlier than usual. The 

 average was more than eighteen days before the earliest previous 

 record. This is borne out by the fact that the same elm (67/«;« 

 inontiina) was in flower this year (on March 9) twenty days 

 earlier than last year. In some cases, e.g. Stellaria Holostea, 

 Ranunculus acris, and Alchemilla vulgaris, the period was 

 increased to as much as five weeks. 



There were a few apparent exceptions, but they may certainly 

 be put down to accident or rather neglect. The chickweeds, 

 Cerastium triviale&nA Stellaria media escaped notice till April, 

 groundsel had previously been noted earlier than April 9, and 

 shepherd's purse was no doubt in flower early in April, but was 

 ignored till May came in. 



The effect of the weather became more pronounced through- 

 out April. Excluding the common "weeds "just mentioned, 

 eve.-y flower was at least a fortnight before its earliest previous 

 record, and the list of twenty-five species is composed almost 

 entirely of May flowers ; in fact the only exceptions were the 

 wood sorrel and the marsh marigold, in flower on the 5th and 

 8th, or antedated fourteen and twenty days respectively. On 

 an average the flowers of April were 25 '5 days earlier than in 

 any of the previous years. The exact dates of a few ol the 

 commonest are appended. 



Cardamine pratensis April 8, 1893; May 10-15, 1887-92 



Scilla nutans ,, 13, ,, ,, i, 1887 



Lychnis diurna ... ,, 13, ,, ,, 10, ,, 



Veronica Chamaedrys ,, 13, ,, ,, 15, 1888 



Allium ursinum .. ,, 16, ,, ,, 5, ,, 



Thirty- five fresh species were added in May, twelve of which 

 are usually June flowers. By this time, however, it became 

 difficult to keep a complete record, so that about half a-dozen 

 appear to flower later this year than in one or other of the 

 previous years. Again excluding these, the remainder flowered 

 seventeen days earlier than before. From a consideration of 

 those given below it would appear that the season was aiout 

 three weeks earlier at the begmning of the month, and a fort- 

 night at the end. 



Cylisus Scoparius ... May 6, 1893; May 13, 1890 

 Orchis mascula ... ,, 6, ,, ,, 14, 1892 



Giraniuui Roberti- 



anuni 6, ,, ,, 17, 18S7 



Trifoliunt praiense ... ,, 6, ,, „ 28. 1892 



Quercus Robur ... ,, 6, ,, ,, 29, 1887 



Crataegus Ojcyacanl ha ,, 7, ,, ,, 29, 1888 



(But usually June 3-9.) 

 Rhinanlhus Crista- 



gain ,, 27, ,, June 9,1890 



C/irysanthemuni 



Leucanlhemum ... ,, 27, ,, ,, 9, ,, 



In June the advance still remained about a fortnight, taking 

 twenty seven species into consideration, but an increasing 

 number have to be left out owing to the impossibility of record- 

 ing all as soon as they appeared. Ten out of the twenty-sev.n 

 had previously belonged to the catalogue of flowers appearing 

 in July. 



Lychnis Fios cuculi ... June to, 1893; June 17-26, 18S7-92 



Silene Cucubaliis ... ,, 10, ,, ,, 26, 18SS 



Rosa canina ,, 10, ,, ,, 28, 1SS7 



Centaurea nigra ... ,, 10, ,, July 2, 18S9 

 Lonicera Periclynie- 



>"">' , IS. ., >> 2, 1892 



Sfiirira Ulinaria ' ... ,, 15, ,, ,, 2, 1889 



Digitalis purpurea .. ,, 15, ,, June 24, 1890 



Valeriana officinal is... ,, 17, ,, ,, 24, ,, 



Achillea millefolium.. ,, 26, ,, „ 27, 1892 



In July there seems to be no evidence for the maintenance of 

 the advance ; the flowers were then appearing at their normal 

 sea-on, e.g. — 



