Hugh Insley a, Lawrence Young b & Brian Dudley c a 1 Minstead Close, Harestock, Winchester, Hampshire b 5 Northfield Farm Cottages, Twy ford,

Transcription

1 This article was downloaded by: [ ] On: 22 March 2014, At: 02:49 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: Registered office: Mortimer House, Mortimer Street, London W1T 3JH, UK Bird Study Publication details, including instructions for authors and subscription information: Primary moult in the Collared Dove Hugh Insley a, Lawrence Young b & Brian Dudley c a 1 Minstead Close, Harestock, Winchester, Hampshire b 5 Northfield Farm Cottages, Twy ford, Hampshire c 2 Fleming Place, Colden Common, Hampshire Published online: 23 Jun To cite this article: Hugh Insley, Lawrence Young & Brian Dudley (1980) Primary moult in the Collared Dove, Bird Study, 27:2, To link to this article: PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the Content ) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any

2 losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at terms-and-conditions

3 Primary moult in the Collared Dove by Hugh Insley, Lawrence Young and Brian Dudley Due to the Collared Dove's extended breeding season, moulting birds may be found in all months. Young birds from late broods often arrest their post-juvenile moult over the midwinter period, and these birds may moult again later in the same year, in line with the moult schedule for adults. LARGE NUMBERS OF COLLARED DOVES Streptopelia decaocto have been trapped by the Lower Test Ringing Group since July 1977 at a poultry farm in Twyford, Hampshire. It was found that during all months of the year some of these birds were in wing moult. Collared Doves are multiple brooded, with a breeding season extending from March to September. The young fledge at about 18 days and leave the nest vicinity at about 21 days (Harrison 1975). The earliest and latest dates on which we have trapped Collared Doves with positive juvenile characters (pale cream fringes to the contour feathers and coverts, brown iris and sometimes the spatulate or squab-shaped bill) have been 18 April and 18 December, giving earliest and latest possible laying dates of 15 March and 14 November. Juveniles begin a complete moult within four weeks of leaving the nest; consequently young birds may be found initiating moult from May to December. Adults also undergo a complete moult each year, so that during every month of the year there are some individuals which are in primary moult. In this paper we describe the primary moult of the Collared Dove from an analysis of 512 individuals caught at Twyford over 15 months in , and from 699 additional moult cards held by the British Trust for Ornithology, which had been collected between 1964 and METHODS Initially, a scatter diagram of primary score (Snow 1967) against date was plotted for all 1,211 cases. This showed that there was a 10 week period from mid- December to the end of February during which no Collared Doves started primary moult; this corresponded with the dates at which the last juveniles to be born in the old year, and the first adults in the new year, started moulting. The 1,211 cards were then sub-divided into those which had been aged by the recorders as juveniles (Euring codes 3J, 3 and 5: 597 cases) and adults (Euring codes 4 and 6: 500 cases). Birds of unknown age (Euring code 2: 114 cases) were dropped from the analysis at this stage. Further, the Lower Test R.G. data were separated from the rest of the BTO collection, because the latter had been gathered over a period of 13 years by 47 ringers operating in widely separated areas of Britain (and therefore were very heterogeneous), while it was clear from the cards that the ageing criteria applied had varied considerably. By comparison, the Lower Test R.G. data were collected by only three ringers using standardised methods for Bird Study 27: , June 1980

4 102 BIRD STUDY a, I / IP /,li a / as a / Ili : a a /7: se 1'. 1 a s / : II Awn Apr May Jun Jul Aug Sep OctNov Oat Jan Feb Figure 1. Scatter diagram and regression of date on primary moult score for all juvenile Collared Doves in the BTO moult card collection. Dotted lines join retraps of the same individual Mar Apr May JUll Jul Aug Sep Oct Nov Dec Figure 2. Scatter diagram and regression of date on primary moult score for juvenile Collared Doves caught at Twyford, Hampshire, between July 1977 and February Dotted lines join retraps of the same individual.

5 COLLARED DOVE MOULT 103 ageing (Insley and Young 1979), and all 512 birds were trapped at a single location (Twyford) within a 15 month period. In the process of sub-dividing the data into these four categories a further 113 cards were rejected. These were birds which were either scored 0 or 50 for primary moult (inclusion of which would have artificially decreased the estimated rate of moult), those showing arrested moult, cases of traumatic moult and cases where either scoring or ageing had obviously been incorrect. The four groups of data were then analysed by calculating the linear regression for date on moult score. RESULTS The scatter diagrams and regression lines calculated for each group of data are shown in Figures 1-4. The regression equations calculated were as follows : BTO data Ages 37, 3 and 5 (182 cases). Date = 4.68 (primary moult score) ; r=0.605 (P=0.001). Ages 4 and 6 (285 cases). Date= 2.58 (primary moult score) ; r=0.603 (P=0.001). Twyford data Ages 3J, 3 and 5 (386 cases). Date= 3.15 (primary moult score) ; r=0.499 (P=-0.001). Ages 4 and 6 (113 cases). Date =1.50 (primary moult score) ; r=0.597 (P=0.001). The differences in ageing techniques used for the BTO and Twyford data were highlighted by the proportions of juveniles in each group. 499 of the 512 Twyford doves were assigned either adult or juvenile status, of which 77.4% were juveniles. The 467 BTO cases used in the analysis contained only 39.0% recorded as juveniles. Timing and duration of primary moult Calculation of the regressions for adult Collared Doves showed that the Twyford sample had a mean starting date of 16 June and a mean completion date of 30 August, giving a total of 75 days for completion of primary moult (0.67 points per day). By comparison, the adults in the BTO collection had mean starting and completion 'dates of 31 May and 7 October, a period of 129 days (0.39 points per day). The longer period shown by the BTO data for doves aged as adults was almost certainly due to the inclusion of a substantial number of incorrectly aged juveniles. The Twyford juveniles showed mean starting and completion dates of 5 July and 9 December, and the BTO juveniles 3 July and 22 February. The mean dates indicated by the BTO juveniles were probably more accurate than those for Twyford, because at Twyford there was a gap in the data from mid-august until early October when each year the Collared Doves left the study area to feed instead on harvested cereal fields.

6 104 BIRD STUDY Apr May Jun Jul Aug Sep Oct Figure 3. Scatter diagram and regression of date on primary moult score for all adult Collared Doves in the BTO moult card collection. Dotted lines join retraps of the same individual..1.-" a I IP = aa' 0,.--*.. E , -....?: -a a al 20 go I II E. I In I Mar Apr May Jun Jul Aug Sep Oct Nov Dec Figure 4. Scatter diagram and regression of date on primary moult score for adult Collared Doves caught at Twyford, Hampshire, between July 1977 and February Dotted lines join retraps of the same individual.

7 COLLARED DOVE MOULT 105 The rate of primary moult for the juvenile population as a whole was reduced by newly fledged individuals initiating moult over the seven months from May to December. This made calculation of the rate from the regressions much less meaningful than for the adults. However, 50 juveniles which were retrapped at Twyford over periods of up to 97 days indicated a mean rate of 0.39 units per day. At this rate, individual doves would require 128 days to complete primary moult. This indication that the rate of moult for adults was faster than for juveniles was quite unexpected, especially since the moult period for adults coincides with the breeding season. Concurrent moult and breeding is exceptional in passerines but does occur with other non-passerines including the Columbidae, eg. Woodpigeon Columba palumbus (Murton 1965). Arrested moult in juveniles During the handling of the Twyford birds and examination of the BTO moult cards, it was discovered that a proportion of juvenile Collared Doves went into arrested moult from late November through to mid-march the following year (Table I). Among the 597 cards for juveniles (BTO and Twyford combined) there were 34 such cases of arrested moult. Some juvenile Woodpigeons also behave in an exactly similar manner at this time of the year (Murton 1965). Although no subsequent retraps of arrested moult birds were available to show the moult sequence on restarting, there was no reason to suppose that moult was not simply restarted from the point reached before the arrest. TABLE I. FREQUENCY OF JUVENILE COLLARED DOVES IN ARRESTED MOULT November December January February March No in arrested moult Total no. of moult cards for juveniles Arrests as % of total Repeated moult in the same calendar year Juveniles undergo a complete moult starting about four weeks after fledging, and adults moult annually, so that all Collared Doves moult each year. However, a few birds may even be in moult twice within the same calendar year. This occurs where juveniles that fledge late in the breeding season do not complete their moult (whether they arrest or not) until early in the following year; then, having finished this complete post-juvenile moult, they moult again during the normal period for adults. Documented cases of this depend upon fairly long-term retraps of birds caught in moult between January and March and then retrapped again between June and September. Although we found that very few Collared Doves were retrapped more than two months after ringing, there were eight cases among the cards analysed demonstrating without any doubt that juveniles which had been In moult early in the year were undergoing a second moult as adults in midsummer. Considering the difficulty of obtaining proven cases from a marked wild population, to have produced eight probably means that this pattern is normal and that all Collared Doves moult as adults during their first post-natal summer (--= second calendar year).

8 106 BIRD STUDY DISCUSSION Several different methods for scoring moult have been used by previous workers. Seel (1976) used a system of feather units based upon the mean dry weight of the whole plumage of each sex of each species. For most feather tracts, he found that the relationship between the accumulation of units (progress of moult) and time was in the form of a sigmoidal curve. However, most other workers have adopted the scoring system used by the BTO Moult Card Scheme (Snow 1967) and, although this may be less accurate than Seel's method, it is much better suited for ringers in the field with limited time available in which to record moult. Equally, although the sigmoidal curve relationship is demonstrable for the progress of moult against time in the feather tracts (the primaries are taken as being representative of moult by most workers) for many passerine species, little precision is lost and the results are much the same if the curved portions at the beginning and end of the moult (which are very short in comparison with the straight line part of the relationship covering most of the moult period) are ignored and the much easier straight line regression is computed. In using regression analysis to examine moult, many previous workers have regressed moult score on time or date. However, this study follows Thomas (1979) in using a linear regression of time on moult score in order to calculate the rate of moult in Collared Doves. Primary moult score was usually recorded more accurately than that for secondaries. The 10 primaries conform with the BTO moult card and are easy to score. By comparison, the 12 secondaries (the reduced 12th is usually omitted) do not conform to the layout of the BTO card, and also become difficult to separate after the 8th or 9th from the tertials and coverts, so that observers varied considerably in their ability to score secondary moult. Hence, although secondary moult score was recorded on the BTO moult cards, the only analysis carried out was the determination of its starting point in relation to primary moult. This showed that initiation of secondary moult coincided wtih the moulting of the 5th primary in both adults and juveniles. Scatter diagrams were plotted for weight on moult score for both juveniles and adults. These confirmed that there was no relationship at all in adults and showed a rather spurious positive relationship in juveniles. With the latter this was probably because the juveniles continued to increase weight, from around 140 g at fledging to around 200 g as adults, and this increase overlapped the post-juvenile moult period. This, together with the fact that adult moult coincides with the breeding season, demonstrates that in Collared Doves moult imposes little of the physiological stress that it is claimed to do in some species. ACKNOWLEDGEMENTS Our thanks are due to the ringers who have completed moult cards for the Collared Dove, particularly five main contributors : Lower Test Ringing Group, J. Sorensen, P. J. Chadwick, C. Lachlan and R. E. Scott. The BTO kindly loaned its moult cards for analysis, while H. B. Ginn and Dr D. K. Thomas gave helpful and constructive criticism of an early draft of this paper. S. J. D. Humphrey Holdings Ltd. have been instrumental in this study by allowing us to trap Collared Doves on their farm at Twyford.

9 COLLARED DOVE MOULT 107 SUMMARY Analysis of 1,211 moult cards for Collared Doves, collected between 1964 and 1978, showed that all have a complete annual moult and that some young birds may be in moult twice during a single calendar year. Data collected at Twyford, Hampshire, over a 15 month period in 1977 and 1978 showed that adult doves had mean starting and completion dates for primary moult of 16 June and 30 August (=75 day period), thus averaging 0.67 units per day. The BTO data for adults were probably less accurate because of the inclusion of some incorrectly aged juveniles (which had the effect of extending the moult period); these gave mean dates of 31 May and 7 October, a period of 129 days and a rate of 0.39 units per day. The mean dates for juveniles at Twyford and from the BTO data corresponded much better, although Twyford data were imbalanced by a gap from mid-august to early October. Mean starting dates were 5 July and 3 July and for completion were 9 December and 22 February (Twyford and BTO collections respectively). The mean rate of moult for individual juvenile Collared Doves was calculated from 50 birds retrapped at Twyford over periods of up to 97 days apart; these indicated that 128 days were required for the completion of primary moult, at a rate of 0.39 units per day. It was found that some juveniles enter a period of arrested moult between November and March; the proportion increased from 9.8% in November to a peak of 51.4% in January, declining to 14.3% in March. The period of moult for adults coincides with the breeding season, and there is no evidence that moult imposes physiological stress upon either adults or juveniles. REFERENCES HARRISON, C A Field Guide to the Nests, Eggs and Nestlings of European Birds. London. INSLEY, H. and L. YOUNG Ageing Collared Doves. Ringers' Bulletin 5: MURTON, R. K The Wood Pigeon. London. SEEL, D. C Moult in five species of Corvidae in Britain. Ibis 118: SNOW, D. w A guide to moult in British birds. 13TO Guide 11. Tring. THOMAS, D. K Wing moult in the Fan-tailed Warbler. Ringing and Migration 2: Hugh Insley, 1 Minstead Close, Harestock, Winchester, Hampshire. Lawrence Young, 5 Northfield Farm Cottages, Twy ford, Hampshire. Brian Dudley, 2 Fleming Place, Colden Common, Hampshire. (Revised MS. received 4 February 1980)