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Repeatability of nest morphology in African weaver

Citation for published version: Walsh, PT, Hansell, M, Borello, WD & Healy, SD 2010, 'Repeatability of nest morphology in African weaver birds' Biology letters, vol 6, no. 2, pp. 149-151. DOI: 10.1098/rsbl.2009.0664

Digital Object Identifier (DOI): 10.1098/rsbl.2009.0664

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Download date: 28. Apr. 2017 ARTICLE IN PRESS

Biol. Lett. (2009) 0, 1–3 variation in a trait (e.g. Lessells & Boag 1987 ; Boake doi:10.1098 /rsbl.2009.0664 1989). As such, it has been used to demonstrate sig- 1 Published online 00 Month 0000 nificant potential for genetic control over nest 65 2 behaviour building in sticklebacks, penduline tits and barn swal- 66 3 lows ( Schleicher et al . 1996 ; Moller 2005; Rushbrook 67 4 et al . 2008 ). The other side of the construction coin 68 5 Repeatability of nest is the contribution made by previous experience, 69 6 including that associated with learning and memory 70 7 morphology in African (Healy et al . 2008 ). Little is known about the impor- 71 8 tance of experience, but it is from weaver birds that 72 9 weaverbirds there is most evidence for a role for experience in chan- 73 10 74 Q1 Patrick T. Walsh 1,2, *, Mike Hansell 3, Wendy ging nest structure: the nests of first-year males are 11 75 D. Borello 4 and Susan D. Healy 1,2 untidy and loosely woven compared with those of 12 76 1 2 mature males ( Collias & Collias 1964 ). It is unclear, 13 School of Biology and School of Psychology, University of Saint 77 Andrews, Saint Andrews, UK however, to what extent the variability of weaver 14 3Division of Environmental and Evolutionary Biology, University of nests may be genetic in origin. 78 15 Glasgow, Glasgow, UK In order to determine the repeatability of nest mor- 79 4 16 Q2 PO Box 603, Gaborone, Botswana phology (width, length and height) in solitary weaver 80 *Author for correspondence ([email protected] ). 17 birds, we collected series of nests built by male 81 18 It is generally assumed that birds build nests Southern Masked weavers velatus in Botswana 82 19 according to a genetic ‘template’, little influ- and by the larger bodied male Village weavers Ploceus 83 20 enced by learning or memory. One way to cucullatus in Nigeria. 84 21 confirm the role of genetics in nest building is 85 22 to assess the repeatability of nest morphology 86 with repeated nest attempts. Solitary weaver 23 87 birds, which build multiple nests in a single 2. MATERIAL AND METHODS 24 breeding season, are a useful group with which Completed nests were collected (November–December 2008) from 88 25 colour-ringed Southern Masked weavers in south-eastern Botswana 89 to do this. Here we show that repeatability of (Atholl Holme 11-KO, Gaborone) approximately 30 days after 26 nest morphology was low, but significant, in they were built. By this time the chicks had fledged. In total, 66 90 27 male Southern Masked weaver birds and not sig- nests were collected: three to eight (mean + s.e.m.: 4.71 + 0.40) 91 28 nificant in the Village weavers. The larger bodied nests each for 14 different males. We used wing length (11 of the 92 14 males) as a proxy of male body size ( Gosler et al . 1998 ). 29 Village weavers built larger nests than did 93 We also collected 27 nests (June–July 2008) from Village weavers 30 Southern Masked weavers, but body size did not in central Nigeria (Laminga Village, Jos, Nigeria), after males com- 94 31 explain variation in Southern Masked weaver pleted building the nest: three to six (4.33 + 0.42) nests each for 95 32 nest dimensions. Nests built by the same male six males. No body size measurements were available for the Village 96 weavers. 33 in both got shorter and lighter as more 97 nests were constructed. While these data demon- For both species, the order in which the nests were built was 34 strate the potential for a genetic component of determined by periodic observation of males’ territories, daily in 98 35 variation in nest building in solitary weavers, it the case of the Southern Masked weavers and three times a week 99 36 for Village weavers. However, as some nests were destroyed before 100 is also clear that there remains plenty of scope collection, the nest data are analysed in sequential, rather than 37 in both of these species for experience to shape numerical, order. 101 38 nest construction. To measure each nest, digital images were captured using a 10 102 39 mega-pixel digital camera and analysed using image analysing soft- 103 Keywords: experience; nest building; repeatability; ware (Measuring Vegetation Health). Photographs were taken from 40 104 weaver bird a camera on a fixed tripod, with each nest placed 1 m away in 41 front of A3 (420 Â 297 mm) 1 cm grid graph paper to provide a 105 42 scale for the images. Each nest was photographed from two different 106 43 views: (i) a lateral side (the same side for all nests) provided nest 107 length and height (figure 1 ) and (ii) the posterior side, which 44 1. INTRODUCTION provided the nest width. Each nest was measured four times with 108 45 Nest building in birds is a widespread, commonly the mean value used in the analyses. Nests were weighed using an 109 46 observed behaviour, and yet we understand rather electronic balance (+0.1 g). 110 The date of nest construction and the sequential order in which 47 little about how birds construct what appear to be 111 the nests were constructed were highly correlated ( r ¼ 0.62, p , 48 species-specific nests. Simple, stereotyped building 0.0001), so Pratt’s measure of relative importance (PRI; Pratt 1987 ) 112 49 rules seem to explain even seemingly complex con- was used to determine that nest order (PRI ¼ 1.156) was substantially 113 ¼ 2 50 structions in invertebrates ( Hansell 2005), but how more important than was date of construction (PRI 0.156). 114 Therefore, analyses of nest size included sequential nest order rather 51 relevant such rules are to avian nest construction is than date of construction. The repeatability of nest size within males 115 52 unclear. While it is generally assumed that nest build- and species was analysed using the three nest size variables in a 116 53 ing in birds is largely innate (e.g. Hansell 2000; Moller multivariate ANOSIM (ANalysis Of SIMilarity), with 10 000 permu- 117 tations, in the PAST statistical package ( Harper 1999 ). Variation 54 2005; Raby & Clayton 2009 ), there are some species 118 among males was determined using linear mixed models, in SPSS 55 that build nests that seem beyond such simple rule- v. 17, with nests as a repeated measure and male as a random 119 56 governed, innate construction. Striking examples factor. Analyses were performed on log-transformed data. 120 57 come from the weaverbirds (Family ), 121 58 which weave and knot plant material in a way that 122 59 has been likened to weaving in humans ( Collias & 3. RESULTS 123 60 Q3 Collias 1964). The length (L) and width ( W ) ( L: F13,51 ¼ 2.32, p , 124 61 A key to understanding how nest construction is 0.05; W: F13,51 ¼ 3.26, p , 0.005; figure 2a) of nests 125 62 achieved is to determine the degree of repeatability of constructed by Southern Masked weavers varied 126 63 nest morphology, as repeatability sets an upper limit across males, but nest height ( H ) did not ( F13,51 ¼ 127 64 on the heritability of a trait, i.e. the potential genetic 1.410, p ¼ 0.19). The dimensions of nests built by 128

Received 13 August 2009 Accepted 28 September 2009 1 This journal is q 2009 The Royal Society rsbl20090664—7/10/09—11:22–Copy Edited by: Chitra S ARTICLE IN PRESS 2 P. T. Walsh et al. Repeatability of nest morphology

129 weaver nests. Village weavers, the larger of the two 193 130 species (Hockey et al . 2005 ), built nests that are 194 131 larger in all three dimensions (length, width and 195 132 height) and heavier than those built by Southern 196 133 Masked weavers. In both species, nest length 197 134 decreased across the season, a decrease that was, in 198 135 Southern Masked weavers, independent of the total 199 136 number of nests built and of body size. 200 137 The repeatability of nest dimensions in Southern 201 138 Masked weavers confirms that there is potential for a 202 139 genetic component to nest building in these birds, as 203 140 seen with nest size (measured from top to bottom) in 204 141 penduline tits (Schleicher et al . 1996 ). However, as 205 142 repeatability was only 0.21 in Southern Masked wea- 206 143 vers and 0.06 in Village weavers, there remains 207 144 considerable within-male variation in both species, 208 145 and with it scope for plasticity in the face of nest- 209 146 building experience. Nest construction in Village 210 147 Figure 1. A series of six nests from a single Southern Masked weavers, especially, may be considerably more respon- 211 148 weaver male (ordered by date of construction from left to sive to environmental influences than is typically 212 149 right). considered to be the case for nest building in birds. 213 150 Indeed, repeatability itself may be a reflection of a 214 151 learning process such as imprinting, as copying of 215 152 the same male were significantly repeatable ( R ¼ 0.21, parental nest building could also lead to greater 216 153 p , 0.0001). Neither variation in nest size among among- than within-male variation in nest dimensions. 217 154 males nor number of nests was explained by body Unlike penduline tits, which build relatively com- 218 155 plex nests that do not vary systematically across the 219 size (L: F1,10 ¼ 0.31, p ¼ 0.59; W: F1,10 ¼ 0.35, p ¼ 156 season (Schleicher et al . 1996 ), nests in both weaver 220 0.57; number of nests: F1,10 ¼ 2.28, p ¼ 0.17). Nests 157 were marginally, but not significantly, different in species changed as the male constructed more nests: 221 158 they got shorter in both length and height and 222 weight among males ( F13,51 ¼ 1.71, p ¼ 0.09; mean: 159 33.66 g + 0.66 s.e.). Earlier nests built by male weighed less. This change may be in response to 223 160 Southern Masked weavers were significantly longer changes in the weather conditions, although is not 224 161 in the direction that would be predicted if that 225 (F1,51 ¼ 8.59, p , 0.005) and tended to be heavier 162 response is to enhance thermoregulation (Hoi et al . 226 (F1,51 ¼ 3.17, p ¼ 0.08) and taller (F1,51 ¼ 3.30, p ¼ 163 0.08) than were later nests. Nest width did not vary 1994, 1996) as weaver nests became smaller as rain- 227 164 fall increased and ambient temperature decreased. 228 in this species ( F1,51 ¼ 3.36, p ¼ 0.07). The nest size 165 Alternatively, nest materials may change across the 229 decrease was not explained by wing length ( F1,46 ¼ 166 0.51, p ¼ 0.48) or the total number of nests that a season in such a way that nest construction is altered, 230 167 Southern Masked male constructed in the season a possibility we are currently exploring. Changes in 231 168 the size and weight of nests within the season may 232 (F1,62 ¼ 0.10, p ¼ 0.76). 169 Among males, there was a significant be an indicator of male quality ( Moller 2005 ). 233 170 Although we have not explicitly measured aspects of 234 difference only in nest length ( L: F5,26 ¼ 4.44, p , 171 ‘male quality’, all of the Southern Masked weaver 235 0.01; W: F5,26 ¼ 1.13, p ¼ 0.378; H: F5,26 ¼ 0.92, 172 p ¼ 0.49; figure 2b). The dimensions of nests built by nests we measured were occupied by females that suc- 236 173 individual Village weaver males were not repeatable cessfully raised offspring. In addition, male size, at 237 174 (R ¼ 0.06, p ¼ 0.227). Additionally, nests varied in least in Southern Masked weavers, does not explain 238 175 the sequential decrease in nest size, as the nests of 239 weight across males ( F5,26 ¼ 3.79, p , 0.05; mean: 176 50.83 g + 2.65 s.e.). The earlier nests of Village all the males decreased and the decrease was indepen- 240 177 dent of the number of nests build by each male. 241 weavers were longer ( F1,26 ¼ 7.20, p , 0.05) and 178 Rather, it seems plausible that increasing nest- 242 heavier (F1,26 ¼ 5.94, p , 0.05) and tended to be 179 building experience leads to smaller nests. This 243 taller (F1,26 ¼ 3.44, p ¼ 0.08) than were later nests. 180 interpretation may be consistent with the observation 244 Nest width did not vary with nest order ( F1,26 ¼ 181 0.35, p ¼ 0.56). that experience leads to changes in nest structure in 245 182 The nests constructed by Village weavers were sig- Village weavers in captivity: first-year male Village 246 183 weavers build loose nests compared with the compact, 247 nificantly longer (F1,92 ¼ 15.71, p , 0.0001), wider 184 tightly woven nests made by older, experienced males 248 (F1,92 ¼ 246.43, p , 0.0001), taller (F1,92 ¼ 156.29, 185 (Collias & Collias 1964 ). 249 p , 0.0001) and heavier ( F1,92 ¼ 76.91, p , 0.0001) 186 than were the nests of the smaller Southern Masked In conclusion, although the repeatability of the 250 187 weavers. dimensions of the complex nests of Southern Masked 251 188 weaver birds is significant, the nests built by solitary 252 189 weavers owe considerably more to the birds’ experi- 253 190 4. DISCUSSION ence of their environment, physical and /or social, 254 191 Repeatability of nest dimensions was significant in than has been previously considered. This leaves 255 192 male Southern Masked weaver nests but not in Village open the possibility that nest construction by weaver 256

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257 20 ( a) ( b) 321 258 19 322 259 18 323 260 324 17 261 325 262 16 326 263 15 327 264 14 328 265 13 329 266 330 11

267 nest measurement (cm) 331 268 12 332 269 10 333 270 9 334 271 1 2 3 4 5 6 7 8 9 10 11 12 13 14 1 2 3 4 5 6 335 272 male male 336 273 Figure 2. Mean ( + s.e.m.) length (filled circles), width (open circles) and height (filled triangles) of nests built by ( a) male 337 274 Southern Masked weavers ( n ¼ 14) and (b) male Village weavers ( n ¼ 6). 338 275 339 276 340 277 birds requires cognitive abilities not dissimilar to those Healy, S., Walsh, P. & Hansell, M. 2008 Nest building by 341 278 used in behaviours currently described as requiring birds. Curr. Biol. 18 , R271–R273. ( doi:10.1016/j.cub. 342 279 ‘physical cognition’ such as tool construction and 2008.01.020) 343 Hockey, P. A. R., Dean, W. R. J. & Ryan, P. G. 2005 280 tool use (Seed et al . 2006 ; Healy et al . 2008 ; Bird & Roberts 344 Birds of Southern Africa . Cape Town, South Africa: 281 Emery 2009 ). 345 Trustees of the John Voelcker Bird Book Fund. 282 346 Hoi, H., Schleicher, B. & Valera, F. 1994 Female mate choice 283 We thank Remi Borello and APLORI for support and the 347 Leverhulme Trust for funding. Permission provided by the and nest desertion in penduline tits, Remiz pendulinus: the 284 348 Botswana Department of Wildlife and National Parks and importance of nest quality. Anim. Behav. 48 , 743–746. 285 the Nigerian Conservation Trust. This manuscript was (doi:10.1006/anbe.1994.1296) 349 286 helped by comments from Dave Shuker and an anonymous Hoi, H., Schleicher, B. & Valera, F. 1996 Nest size variation 350 287 reviewer. and its importance for mate choice in peduline tits, Remiz 351 288 pendulinus. Anim. Behav. 51 , 464–466. ( doi:10.1006/ 352 289 anbe.1996.0046) 353 290 Lessells, C. M. & Boag, P. T. 1987 Unrepeatable 354 repeatabilities: a common mistake. Auk 104, 116–121. 291 Bird, C. D. & Emery, N. J. 2009 Insightful problem solving 355 Moller, A. P. 2005 Rapid change in nest size of a bird related 292 and creative tool modification by captive nontool-using 356 to change in a secondary sexual character. Behav. Ecol. 17 , 293 rooks. Proc. Natl Acad. Sci. USA 106, 10 370–10 375. 357 108–116. ( doi:10.1093/beheco/arj003) (doi:10.1073/pnas.0901008106) 294 Pratt, J. W. 1987 Dividing the indivisible: using simple sym- 358 Boake, C. R. B. 1989 Repeatability: its role in evolutionary 295 metry to partition variance explained. In Proceedings of the 359 studies of mating behavior. Evol. Ecol. 3, 173–182. 296 second international conference in statistics (eds T. Pukkila & 360 (doi:10.1007/BF02270919) 297 S. Puntanen), pp. 245–260. Tampere, Finland: 361 Collias, E. C. & Collias, N. E. 1964 The develop- University of Tampere. 298 ment of nest-building behavior in a weaverbird. Auk 81 , 362 Raby, C. R. & Clayton, N. S. 2009 Prospective cognition in 299 42–52. 363 . Behav. Process. 80 , 314–324. ( doi:10.1016/j. 300 Gosler, A. G., Greenwood, J. J. D., Baker, J. K. & Davidson, 364 beproc.2008.12.005) 301 N. C. 1998 The field determination of body size and con- 365 Rushbrook, B. J., Dingemanse, N. J. & Barber, I. 2008 302 dition in : a report to the British Ringing 366 Repeatability in nest construction by male three-spined 303 Committee. Bird Study 45 , 92–103. ( doi:10.1080/ 367 sticklebacks. Anim. Behav. 75 , 547–553. ( doi:10.1016/ 00063659809461082) 304 j.anbehav.2007.06.011 ) 368 Hansell, M. 2000 Bird nests and construction behaviour . 305 Schleicher, B., Hoi, H. & Valera, F. 1996 Seasonal change in 369 Cambridge, UK: Cambridge University Press. 306 female mate choice criteria in Penduline tits ( Remiz 370 Hansell, M. 2005 Animal architecture. Oxford, UK: Oxford 307 pendulinus). Ardeola 43 , 19–29. 371 University Press. 308 Seed, A. M., Tebbich, S., Emery, N. J. & Clayton, N. S. 2006 372 Harper, D. A. T. 1999 Numerical palaeobiology: computer- Investigating physical cognition in rooks Corvus frugilegus . 309 based modelling and analysis of fossils and their distributions . 373 Curr. Biol. 16 , 697–701. ( doi:10.1016/j.cub.2006.02. 310 Chichester, UK: John Wiley & Sons. 374 311 066) 375 312 376 313 377 314 378 315 379 316 380 317 381 318 382 319 383 320 384

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