DISCUSSIONS

REPORT O N T H E PHENOLOGICAL OBSERVATIONS I N THE BRITISH ISLES FOR OCTOBER 1946 TO

SEPTEMBER 1947 (April 14, 1948)

DISCUSSION

Mr. GORDON MANLEY (in the Chair): I am asked to cxprcss thc President’s regret that he is unavoidably absent and to read his letter :

“ I am very sorry that 1 cannot be present this afternoon nhen h‘lajor Gunton presents his Phenological report, and that I cannot express my personal admiration of his work and the cnormous labour mhich he has put into this work throughout the past eleven years.

Then, as President of the Society I should have lilted to convcy to him on behalf of every Fellow their thanks for all he ha5 done for the Society as its Phenological Director. As you know, thc Socicty recently tried to show its admiration of Major Gunton’s work b j malting him the first award of the Darton PriLe for the most valuablc digest of observations of significance and use to meteorology published by the Society i n the previous twelve months. When Major Gunton now rctires froin the position of Phenologital Director, 1 am sure he will still keep his interest in the work and I may express the hope that he will do, what perhaps only he can do, namely present to the Society in broad outline an account of all that has been learnt from the many years of regular observations.

I can only conclude by again acknowledging thr Socictp’s gtcat debt to Major Gunton for his clcvcn years’ work as Phenological Director.” Mr G O K D O ~ ~ ~ M A ~ L E Y : I should like to take this opportunity of

supporting thr l’rrsidcnt’s remarks and to say how much wc look forward to hearing Major Gunton’s report.

Major H. C. Gwlriiov, in presenting his elevcnth and last Phenolo~ic,il Report, began by paying a tribute to the corps of observers by whosc efforts it had been possible to maintain the Rcport through the war years with only slight reduction in numbers. He explained by means of a slide the outstanding fcatures of a remarkable year, dra\ving particular attention to the importance of the life higtorics and habits of insects in determining the effectr of meteorological conditions including drought. An additional slide illustrated the general similal ity in thr weather arid its effects in 1942 and 1947. After explaining the diagrami dealing with three aspects of divergence over a number of ycars, thc variations i n the earliest dates on a district basis, those of different stations in the same district and those of i n c h idual stations, he slio\ccd somc additional slidcs in order to demonstrate care and atcuracy on thtl part of the observers.

Mr. GORDON MANI EY : [Ye have hcard Major Gunton’s presentation of this, the final Report under his direction. Before asking for contri-

168

DISCUSSIONS 169

butions to discussion I should like to say how much the Society owes to Major Gunton for his really remarkable accomplishment in compiling again so succinct a summary of the great mass of painstaking observa- tions sent in by this widespread body of enthusiastic contributors. Scattered as they are over the whole of the British Isles, I might well add a s a geographer how much I can appreciate the effort involved in the integration of so much material and the ingenious and concise diagrammatic methods used.

Dr. C B. WILLrilnis (President, Royal Entomological Society) : 1 congratulate Major Gunton on the new Phenological Report, and much regret that it seems likely to be the last of the series produced by the Koyal Meteorological Society. We have found at Rothamsted that the number of insects in that district seems to be determined chiefly by rainfall in the summer months and by temperature in the winter. But the earliness and latenes5 is determined almost entirely by temperature.

I n reply to a remark by Mr. Bonacina, Dr. Williams also said: Many year5 ago I made a study of Hopkins’s “Bio-climatic l a m ” and came to the conclusion that in the Mississippi Valley, where they nere first establi,hed, they represented the average rate of movement of the isotherms in the spring. Temperature was the most important phenological factor in that area and so events tended to follow the isotherms. \\;hen the movements of the isotherms differed from Hopkins’s Laws, then the phenological events also differed from them. Thus the isotherms n ere-

Dr. .I. E. 51 I\TEII : -1 few days ago, looking through an old volume of A’ature (1926, Vol 117, p.~~g), I came across a phenological map of Russia showing the northward spread of the cuckoo (Cucztlus Canorcrs) in the spring of 1924. .I striking feature of the map is the rapid spread between .Ipril 20 and May I along a narro\v band of country passing through Moscow tonards the N N E . , amounting to some 1,000 miles in I I days. The authoi, P. J. Schmidt, states that cyclonic conditions broke in from the north-we\t a t this time, giving strong southerly xvinds along this particular track, while there nere northerly winds to east and west of it, where the spread of the cuckoo \xas held up. Honever, as the rate of the unusually fast northward spread works out a t less than 4 miles an hour, it cannot be claimed that the curkoos were borne along passively by the strong winds. In fact, as Landshrough ‘Thompson says, migrating birds prefer to avoid strong following winds, though they will readil! start a migration flight in a light contrary wind. The most plausible explanation, he states, is that strong winds usually mean cyclonic conditions, when a bird starting in a favourable nind might soon find itself in an equally strong nind blowing in the wrong direction ; whereas light winds probably indicate anticyclonic conditions over a large area, when a bird has a better chance of reaching its destination, even if much of the flight is against the wind.

I t is interesting to see whether the present Phenological Report can 5hed any light on these ideas. The average date for first hearing of the cuckoo is given as day 91 for southern England, 98 for the north, and 108 for Scotland. Plotting the data given for the cuckoo in 1947, M e find that its arrival was in general about a fortnight later. Yet there were strong southerly cyclonic winds blowing from southern Spain to England on March 26, 27 and 28 (days 85 to 87), but only a single observation is reported at that time, a t Ruddington in the east Midlands on day 87.

.over a large area-a better guide than Hopkins’s Laws.

170 DISCUSSIONS

This \vas follo\vetl by 4 days of moderate westerly \vinds, after \vliich anticyclonic conditions set in along the migration route and persisted almost without a break for three weeks. Apart from isolated reports on days c , j antl 07 from the east coast a n d d:iy g8 in the north, the cucl;oos arrived over inost of rcntral mid sr)uthcrn ISnglund between days ~ o o and I 10 (.lpriI 10 to L O ) during the latter half of this anticyclonic spell, having apparently Ivaited till \veil after the southerly gale had bloivn itself out.

Mr. 0. M. . \ S I I I W ~ ~ D : ,\lrrition has been nindc, of the rllect of strong uintls in delaying the% arrival o f niigratory birds in the spring. 1 t tias recently bcrn suggested by Yeag1c.y ( lo t~rna l of Afifilied physic:^, Val. 18, N o . 12, I k e m b e r 1~147, pp. 1035-1063) that pigcons niivigatc by being sensitive to Coriolis force and the vertical coniponcnt of tlie earth’s magnetic licld. l’hr r f f c c t of strong \\.incls is csplainrd by the increased difficulty for the birds to iiieasiire (:oi-iolis force ririder these circuinstmces. Severe niagnctic stornis \ ~ o u l d also increase the birds’ navigation tliffi- culties and it might be Lvorth investigating tlie correlation bet\veen the date o f arrival o f birds and the tlcgrcc of m;ignotic disturbance. I t woultl be very interesting i f :in I I-!’c.;ir cycle follo\ving the cyclr ol magnetic stnrnis could lor ehtablishctl. I t srcriis very probable, I~ouc~vcr , that the effect of niagnctic stornis \\.auld be complrtc~ly masli t4 by tlic influcxricc of {vcather conditions.

Mr. I.. C 7 . \V. B o s . \ c r ~ a : Having spulwn on each of Major Gunton’s , tcn prtlvious Reports I an1 ;msious not to let the soiiie\vIi:it sad occitsion of his final :ippearance pass n.itliout athliiig a few further remarks. 1 think lie i, to hc rongratulated particularly upon having ;icconiplished so much to clarify tlie clecidrdly involved theory of the subjt1c.t \vliic.li shuulcl certain1 . prove ‘helpful to \vha t rvr r authority carries on this \vork.

mnttrr o f tlivwgrncr \vliicli he has strcsscd s o much i n caii ie ;~ci-os-s an outst:inding case myself in Fehi-wiry ot

the prcwnt ycar 1048. I3y the inidtlle of tlic month the almond blossom \vas \yell O L I ~ i n this part of I.ondon, namely Kensington, but \vas only

in Hi in ips t rad , w h r w I live, \\hen the suddrn by ciiusiiig ;I divcrg:cnrc of sonie three u.eelts

One frequently hears pc~tp le asking \vhethcr plienolog-y should be rcg:irtic:d ;is meteorology (clim;itology) or :IS biology whcii its very question pi-rtty obviously implies that it is both. I t is ;I p:irt of the very iniportant coming scicwcc, o f bio-c liinatolop.. I do not u:rnt to piit :I

“posw” to this meeting hut 1 soinrtiiiit~s \vonclcred how much o f d i i i t a k would really be lcft i f it \verc tlivorcrtl from the bodily antl mentul reactions of living org:inisms. I n .\merica Hopkins 1x1s done a very good deal of work on the bin-climatic function o f phcnology, and hc formu- lated :I “bio-climatic l a ~ ~ ” according to xvliirh the spriiic retards 4 t1:iys for every I dec-ref of latitude nctrthtvard, 4 days for every 400 feet upunrci, and i n the northern hcmisphcrc 4 days f o r every j degrees of longitude easttvard. W h a t wc now necd is the formulation of a more exact law n-hich \ x ~ ~ l d involve l inking up tlic phcnological survey of the Rritisli Isles ivitli that of continental countries.

T h e Major spoke of the nuiiierous clouded-yellow butterflics in 1y47 and I should like to record niy surprise a t seeing one flitting about :I

bombed ruin in the middle of E w t e r last September.

DlSCUSSIONS 171

Mr. E. L. H A w K E : .\s Mr. Bonacina has said, it is sad that the excellent Report before us is to be Major Gunton’s last. In offering hiin cordial congratulations on it I would subscribc to the hope expressed by the l’resident t ha t Major Gunton will prepare for us a paper presenting the main conclusions Lvhich he has reached as a result of his 1 1 years’ intensive study of phenology through the medium of the Society’s records. Such a summary, put together by ou r highest authority on the subject, lvould be most valuable and \vould tittingly crown the fine work that

I t is interesting to compare some of last year’s early phenological events g-iven in the table of Marsham observations on p. 17 of the Report \\ ith the corresponding records for previous seasons that follo\vcd very sevcre \\,inters. T h e date of March 13 for the first appearance of the stio\vdi-op is the latest ever chronicled by a margin of three weeks; the ncnrest approaches Lvere February z I and February 19 after the memorably hard \viiiters of 1939-40 and i#q-( j j respectively. Another extremely late event last spr ing Tvas the hatching of yourig. roolts. According to the I\larsharn data they did not shuiv themselves until May I I . Th i s too is the latest date in a record which, with a few gaps, extends over more than t\vo centuries. I t is a pity that there are no Marsham observatioiis lor 1814, as that seeins to have been the last year in which England as a \vholc had a continuous sno\v-cover persisting for so l ong as it did during the early stages of 1947.

Mr. L. C . W. BONACINA: I take exception to a point raised by Mr. H a x l c e .concerning snoxvfall. T h e tvhole of the British Isles lay continuously under sno\v for just as long a period in 189; as in 1947, from about January 22 to March 6 in the former year and January 25 to March 10 in the latter. I t is true the amount of snow which fell in 1 8 g j was much smaller in eastern and midland England than in 1947, but it was very great in Scotland, northern England, the Isle of Man and Ireland as well ;IS in parts of Watcs and south-west England. In 1890-91 southern and Inidland England lay continuously under snow from about November 28 to January 2 1 , a longer period than in either ~ S q j or 1947, but the cover did not extciid north of about York according to travellers betlveen London and Edinburgh.

Mr. GOKDON MANLEY: Mr. Bonacina \\’as there to see the 189.; sno\\- a n d \ve should congratulate h i m ; but I do not think he could have seen that of 18;8-~), \vhich in many districts \vas probably the most persistently sno\\:y \\ inter for ninety years. Froin the north-east coast Backhouse’s record ncar Sunderland covered 1857-191s. H e noted sixty-three days a.ith sno\v-cover in 187S-9, forty-six in 1880-1, thirty-nine in 18j9-60 and iXgg-1900, thirty-eight in 1874-j, thirty-seven in 1894-5, thirty-six in 18Sj-6. By his standards I should estimate fifty for 1916-17 and sixty for 1946-7 to be the two highest totals since 1912.

I have no qualifications on the biological side; but Mr. Hawlre’s refei-ence to the Marsham record tempts me to speak of the value of phenological da t a in another direction. I took out the mean date of the 16 cvents, omitt ing the snoLvdrops, for the periods 1751-85 and 1891-1925. Now although the record of individual events may be imperfect for a variety of reasons, when you are dealing with 16 events arranged over 3 j years the resultant index of the mean temperature of the months March-May for the period is probably good. Hence as the temperature trend for Norfolk is not likelv to differ seriously from that

jor Gunton has done for the Society.

I72 DISCUSSlONS

for Lancashire, I took out the March-May overall mean for each group of years. I am bound to say that I find the resultant overall accordancc very tempting as a broad confirmation of the estimates I made for the period belore 1781. Eighteenth-century temperature series are so few, and the instruments and exposures were so faulty that one must lean on all kinds of support for purposes of checking: and when 1 found that for 1751-85 the mean temperature of the 3-month period in question \\a5 46” and the mean date for all the 16 events ..\pril 13, uhile for 1891-192s I had 46.2” and April 1 2 , it seemed that no serious error in the reductions should exist. The range of variability of the English spring a t different localities, and perhaps evcn more that of Scotland is undoubtedly one of the most interesting Features of our climate.

Major H. C. GUNTON (an rep ly ) : I think that there are very few points in this interesting disrusqion which call for any further observations by me.

Dr. Slater, referring to the dates of arrival of the cuckoo, appears to have misapplied, inadvertently, the average dates given at the end of Table V I I I ; these are the average earltest dates, referring to the arrival of the “vanguard” in each of three zones and with theni should be compared only the corresponding earlzest dates in 1947, as shown in the inset graph in Fig. I and which does not indicate any lateness on this basis. Neither do dates for the main body varying between days ion and I 10 suggest any appreciable departure from the usual regularity of this migrant.

I mas very glad to hear Mr. Bonarina dispose of the doubts of those u ho have regarded meteorology and biologl as alternatives rather than as inextricable concomitants in relation to phenology, a.; in the n ider field of bioclimatics.

With regard to the President’s message which I deeply appreciate, I n i l 1 certainly consider a contribution summarising what has been learnt from these Reports. Incidentally, I u elcome the suggestion a5 an opportunity of showing my gratitude for the support and appreciation extended to me by those, inside and outside this Society, u h o are interested in this subject.

Mr. GORDON MANLEY: In moving the thanks of the meeting to Major Gunton, I should like to call attention to the faithful work of the observers during and throughout the war years. Many indeed founcl relief in the contemplation of the round of nature; yet it w a ~ a remarltnblr accomplishment, for which the Society might be inclined to take credit, that a ful l schedule of records was maintained unbroken through that period. But for this the credit is overwhelmingly due to Major Gunton, and on thc eve of his retirement I should like to pay a tribute on behalf of of many younger men to his determination, assiduity, and care. Indeed a fine example has been set for others who might be tempted to allow the existence of a state of war to discourage their efforts. Several Fellons had asked about the outlook for the future; I can assure theni that phenology is the concern of many and that the Society has the matter under active consideration in connexinn with the intcrrsted bodies; I am glad to be able to say that an announcement may be expected a t no distant date.