Juvenile Plumage Whiteness Is Associated with the Evolution Of

Home , Montifringilla

1 Juvenile plumage whiteness is associated with the

2 evolution of clutch size in passerines

4 Running header: juvenile signals and family size

7 Judith Morales1*, José Javier Cuervo1, Juan Moreno1 and Juan José Soler2

9 Running header: juvenile signals and family size

11 1National Museum of Natural Sciences (MNCN-CSIC), c/ José Gutiérrez Abascal 2,

12 28006 Madrid, Spain

13 2Estación Experimental de Zonas Áridas (EEZA-CSIC), Ctra. de Sacramento s/n, La

14 Cañada de San Urbano, 04120 Almería, Spain

15 *Correspondence: [email protected]; Tel.: +34 914 111 328 (ext. 1341)

17 Fig. A1. Example of selection of juvenile ventral feathers using the magnetic lasso tool in

18 Photoshop (plate from the Complete Birds of the Western Palearctic on CD‐ROM version 1.0

19 (Cramp and Perrins 1998, Oxford University Press, Oxford, UK)).

22 Table S1. Values of juvenile ventral and tail/wing whiteness, mean clutch size, type of nest (open vs. cavity/domed), (log10) female mass (g) and number of

23 broods raised per year (1 = one vs. 2 = more than one) are shown for all the species included in the analyses (n = 210). Data were obtained from The

24 Complete Birds of the Western Palearctic on CD‐ROM version 1.0 (BWP, Cramp and Perrins 1998, Oxford University Press, Oxford, UK), except when marked

25 with a superscript letter. Predation rate (percentage of nests lost due to predation) was available for a reduced set of species (n = 79). If not specified with

26 superscript letters, predation rate was obtained from BWP. When various sources were available, values of different sources were averaged (see the

27 complete list of references below the table).

Species Female Nest Mean Juv. ventral Juv. tail/wing No. Predation

mass type CS whiteness whiteness broods rate

Tchagra senegalus 1.74 open 2.3 159.01 1 1

Oriolus oriolus 1.84 open 3.5 169.43 0 1 7.2

Lanius excubitor 1.83 open 5.5 184.22 2 2

Lanius nubicus 1.38 open 5.5 190.39 2 2 76.9

Lanius schach 1.52 open 5 a 163.02 1 2 a

Lanius collurio 1.51 open 5 145.09 1 1 19.4

Lanius senator 1.57 open 5.5 181.1 1 2

Lanius minor 1.67 open 5.5 194.45 2 1 14.5

Pyrrhocorax pyrrhocorax 2.48 cavity 4 34.84 0 1

Pyrrhocorax graculus 2.32 cavity 4 42.85 0 1

Perisoreus infaustus 1.91 open 3.5 113.38 0 40.9

Garrulus glandarius 2.21 open 6.5 134.06 1 1 31.9

Pica pica 2.3 cavity 6 206.8 1 1 40.5 b

Nucifraga caryocatactes 2.27 open 3.5 138.02 2 1

Corvus rhipidurus 2.75 cavity 3.5 62.07 0 1

Corvus monedula 2.36 cavity 5 56 0 1 32.6 j

Corvus corone 2.71 open 4.5 27.26 0 1

Corvus ruficollis 2.75 open 3.5 53.31 0 1

Corvus frugilegus 2.62 open 4 42.55 0 1

Corvus corax 3.06 open 5 36.46 0 1

Remiz pendulinus 0.95 open 7 203.42 2 2 4.0

Parus cyanus 1.08 cavity 10 172.85 2 1

Parus caeruleus 1.04 cavity 11 175.64 2 1 25.6 b

Parus palustris 1.08 cavity 8 196.68 0 1 47.9 c

Parus major 1.26 cavity 8.5 174.27 1 1 25.5 b

Parus cristatus 1.08 cavity 6 187.97 0 2 47.7 b

Parus ater 0.95 cavity 8.5 167.44 1 2

Parus lugubris 1.2 cavity 8.5 167.31 0 2

Parus montanus 1.04 cavity 7.5 189.92 0 1 46.3 b

Parus cinctus 1.04 cavity 8 159.12 0 1

Panurus biarmicus 1.15 open 6 166.34 2 2

Alaemon alaudipes 1.67 open 3.5 227.26 2 1

Rhamphocoris clotbey 1.65 open 4 211.35 1

Ammomanes deserti 1.4 open 3 226.89 0 2 85.0 h

Eremopterix nigriceps 1.08 open 2.5 228.24 1 1

Ammomanes cinctura 1.26 open 3 227.72 0 2 a

Eremophila bilopha 1.58 open 3 215.57 1 1 a

Eremophila alpestris 1.57 open 3 216.75 1 2 25.5 l

Calandrella brachydactyla 1.34 cavity 4 219.94 2 2 50.0

Calandrella rufescens 1.3 open 4 217.97 2 2

Melanocorypha leucoptera 1.65 open 5.5 214.17 2 2

Melanocorypha bimaculata 1.73 open 4 202.9 2 2

Melanocorypha calandra 1.76 open 4.5 198.6 2 2

Melanocorypha yeltoniensis 1.74 open 5.5 216.09 2 2 a

Lullula arborea 1.51 open 4 222.26 2 2 25.0 g

Alauda arvensis 1.53 open 4 217.05 2 2 60.5 e,f,g

Galerida cristata 1.64 open 4 224.2 1 2 42.9 h

Galerida theklae 1.57 open 3.5 214.73 1 2

Hirundo rupestris 1.3 cavity 4 141.04 1 2

Riparia riparia 1.15 cavity 5 192.48 0 2 41.2

Riparia paludicola 1.08 cavity 3.5 191.48 0

Aegithalos caudatus 0.9 cavity 10 197.65 2 1 31.5 d

Cettia cetti 1.08 open 4.5 132.82 0 2

Phylloscopus trochilus 0.9 cavity 6 208.18 0 2 43.4 b

Phylloscopus collybita 0.9 cavity 5.5 210.58 0 2 28.7 b,c

Pycnonotus xanthopygos 1.64 open 3 164.75 0 2

Prinia gracilis 0.85 open 4.5 204.96 0 2

Cisticola juncidis 1.04 cavity 5 171.96 0 2 21.5 i

Scotocerca inquieta 0.9 open 3.5 213.05 0 2 28.0

Locustella naevia 1.15 open 5.5 158.54 0 2

Locustella luscinioides 1.2 open 4.5 152.71 0 2

Locustella fluviatilis 1.18 open 5.5 171.1 0 1

Hippolais polyglotta 1.11 open 4.5 165.76 0 2

Hippolais icterina 1.11 open 4.5 223.78 0 1

Acrocephalus melanopogon 1.08 open 4 145.1 0 1

Acrocephalus paludicola 1.04 open 5 184.49 0 2

Acrocephalus brevipennis 1.18 open 2.5 173.1 0 2

Acrocephalus arundinaceus 1.45 open 4.5 160.6 0 2 31.6

Turdoides fulva 1.79 open 4.5 168.22 0 2

Turdoides altirostris 1.52 open 3.6 204.16 0 2

Sylvia borin 1.28 open 4.5 163.36 1 1 17.9 b

Sylvia atricapilla 1.28 open 5 143.5 0 2 16.3 b

Sylvia nisoria 1.41 open 4.5 162.48 1 2

Sylvia curruca 1.08 open 5 148.89 1 1 25.9 b

Sylvia leucomelaena 1.18 open 2.5 158.45 0 2

Sylvia hortensis 1.34 open 4 142.1 1 1

Sylvia nana 0.9 open 4.5 149.13 0 2

Sylvia melanothorax 1.04 open 4.5 148.69 1 1

Sylvia rueppelli 1.11 open 4.5 158.64 1 1 a

Sylvia cantillans 0.95 open 3.5 136.19 0 2

Sylvia mystacea 1 open 4.5 135.37 0 1

Sylvia melanocephala 1.08 open 4 144.77 1 2

Sylvia communis 1.15 open 4.5 140.2 1 2 21.3 b

Sylvia conspicillata 1 open 4 178.92 1 2 20.0

Sylvia sarda 1 open 3.5 129.71 1 2

Sylvia undata 1 open 4 117.62 0 2 20.8 b

Sylvia deserticola 0.9 open 4 169.95 0

Regulus regulus 0.78 cavity 10 189.4 1 2

Regulus ignicapilla 0.7 cavity 9.5 189.69 0 2 42.9

Troglodytes troglodytes 0.9 cavity 6.5 105.78 1 2 91.0 c

Tichodroma muraria 1.26 cavity 4.5 138.58 2 1

Certhia familiaris 0.95 cavity 5.5 216.34 1 2 7.1

Certhia brachydactyla 0.95 open 6.5 209.94 0 2 9.0

Sitta tephronota 1.63 cavity 6.5 179.33 0 2

Sitta neumayer 1.48 open 9 194.43 0 2

Sitta europaea 1.36 cavity 8.5 156.44 2 1 29.3 b

Sitta krueperi 1.08 cavity 5.5 116.78 1 1

Sitta whiteheadi 1.08 cavity 6 156 1 2

Onychognathus tristramii 2.08 cavity 3 49.14 0 2

Sturnus unicolor 1.95 cavity 4.5 80.4 0 2

Sturnus vulgaris 1.89 cavity 5 105.6 0 2 24.7 b

Sturnus roseus 1.83 cavity 4.5 188.91 1 1

Acridotheres tristis 2.08 cavity 4.5 109.25 2 2

Sturnus sturninus 1.69 open 5.5 a 199.44 1

Cinclus cinclus 1.83 cavity 4.5 120.16 1 2 13.9 b

Zoothera dauma 2.19 open 4.5 158.42 1 1

Turdus viscivorus 2.09 open 4 162.52 0 2

Turdus philomelos 1.89 open 4 129.08 0 2 87.0 c

Turdus merula 2 open 4 96.36 0 2 65.4 b,c

Turdus iliacus 1.79 open 5 150.5 1 2 43.5 b,o

Turdus pilaris 2.01 open 5.5 161.45 1 2 17.0 o

Turdus ruficollis 1.94 open 5.5 166.26 1 1

Turdus torquatus 2.03 open 4 68.18 1 2 13.0

Tarsiger cyanurus 1.18 cavity 6 170.79 0 2

Erythropygia galactotes 1.36 open 4.5 206.43 1 2 27.8

Erithacus rubecula 1.2 cavity 5 126.97 0 2 22.0 b

Irania gutturalis 1.3 cavity 4.5 198.03 0 1 a 30.2

Luscinia svecica 1.26 open 5.5 175 0 2

Luscinia megarhynchos 1.28 open 4.5 200.83 0 2 7.5 b

Luscinia luscinia 1.4 open 4.5 190.68 0 1

Ficedula hypoleuca 1.08 cavity 6.5 155.02 1 2 64.7 b,c

Ficedula parva 1.08 cavity 5.5 140.02 1 1

Luscinia calliope 1.34 open 5 168.35 0 1

Phoenicurus ochruros 1.18 cavity 5 85.97 0 2

Phoenicurus erythrogastrus 1.4 cavity 4 155 0

Phoenicurus moussieri 1.18 cavity 4.5 148.4 1 1

Phoenicurus phoenicurus 1.18 cavity 6 140.65 0 2

Monticola saxatilis 1.71 cavity 4.5 132.67 0 2

Monticola solitarius 1.76 cavity 4.5 98.13 0 2

Saxicola torquatus 1.18 open 5 183.98 1 2 8.1

Saxicola rubetra 1.23 open 5.5 161.81 2 1

Oenanthe oenanthe 1.38 cavity 5.5 161.1 1 2 28.0

Oenanthe monacha 1.26 cavity 4.0 a 182.54 0

Oenanthe deserti 1.32 cavity 4.5 157.58 1 2

Oenanthe pleschanka 1.28 cavity 5 206.15 1 1

Oenanthe hispanica 1.41 cavity 4.5 212.32 1 2

Cercomela melanura 1.18 cavity 3.5 175.68 1 2 a

Oenanthe leucura 1.58 cavity 4 27.47 1 1 50.6

Oenanthe leucopyga 1.4 cavity 4 42.13 2 2

Oenanthe albonigra 1.41 cavity 4.5 182.45 1 2 a

Oenanthe xanthoprymna 1.34 cavity 5 151.62 0 2

Oenanthe lugens 1.32 cavity 4.5 193.19 2 2

Oenanthe finschii 1.41 cavity 5 209.49 1 2

Nectarinia osea 0.85 open 2 180.17 0 2

Ploceus manyar 1.23 open 2.5 159.64 0 2

Amandava amandava 1 open 5.5 174.02 1 2

Lonchura cantans 1.08 open 4.5 a 204.59 1

Lagonosticta senegala 0.95 cavity 3.5 150.34 0 2

Prunella ocularis 1.3 open 3.5 151.18 0 2 a

Prunella atrogularis 1.28 open 5.5 159.82 1 2

Prunella montanella 1.23 open 5 171.57 0 2 a

Prunella modularis 1.32 open 4 145.15 1 1 15.9 b

Prunella collaris 1.63 cavity 3.5 138.09 2 2

Petronia brachydactyla 1.32 open 4.5 205.32 0 1 85.7

Petronia xanthocollis 1.26 cavity 3.5 226.81 2 2

Petronia petronia 1.51 cavity 5.5 198.02 0 2

Montifringilla nivalis 1.57 cavity 4.5 210.8 2 2

Passer simplex 1.3 cavity 3.5 228.66 0 2

Passer montanus 1.3 cavity 5 201.24 1 2

Passer luteus 1.15 open 4 210.21 0 2 5.5

Passer moabiticus 1.3 open 4.5 207.74 0 2

Passer domesticus 1.48 cavity 4 203.67 0 2 2.8

Passer hispaniolensis 1.41 cavity 5 200.74 0 2

Motacilla cinerea 1.23 cavity 5 183.62 2 2

Motacilla flava 1.2 open 5 170.63 1 1 29.2 b

Motacilla alba 1.3 cavity 5.5 177.47 1 2 21.6 b

Anthus campestris 1.32 open 4.5 194.13 1 1 40.0

Anthus berthelotii 1.2 open 3.5 220.08 2 2

Anthus pratensis 1.3 open 4 222.29 2 2 20.0 b

Anthus petrosus 1.32 cavity 5 169.82 0 2 0.0

Calcarius lapponicus 1.36 open 5.5 186.07 2 1 51.5

Plectrophenax nivalis 1.56 cavity 5 181.85 2 2 14

Emberiza striolata 1.15 cavity 3 180.94 0 2

Emberiza cineracea 1.38 open 5 200.79 2

Emberiza pallasi 1.18 open 4.5 204.35 1 1

Emberiza schoeniclus 1.26 open 4.5 202.96 1 2 52.9

Emberiza pusilla 1.18 open 5 196.47 1 2

Emberiza rustica 1.26 open 4.5 191.41 2 2 20.5

Emberiza melanocephala 1.43 open 4.5 209.15 1 1

Emberiza bruniceps 1.36 open 4.5 194.31 1 2 28.4

Miliaria calandra 1.6 open 5 204.17 1 2

Emberiza cia 1.36 open 4.5 182.98 2 2 43.9

Emberiza buchanani 1.32 open 4.5 170.88 1 1

Emberiza hortulana 1.28 open 4.5 195.11 2 1 32.0

Emberiza cirlus 1.38 open 3.5 207.61 1 2 22.0

Emberiza citrinella 1.43 open 4 204.33 1 2 33.3

Emberiza leucocephalos 1.43 open 4.5 192.48 2 2

Fringilla montifringilla 1.38 open 6 193.89 2 2

Fringilla teydea 1.46 open 2 171.79 1 1 73.9 n

Fringilla coelebs 1.36 open 4.5 181.46 2 1 70.8 b

Coccothraustes coccothraustes 1.72 open 4.5 167.16 2 1

Pinicola enucleator 1.74 open 3.5 169.74 0 1 23.5

Bucanetes githagineus 1.26 cavity 5 209.13 0 2

Eremopsaltria mongolicus 1.34 open 5 198.65 2 2

Carpodacus erythrinus 1.38 open 5 192.16 0 1 30.5

Carpodacus rubicilla 1.66 cavity 4.5 173.37 1 1

Carpodacus synoicus 1.32 cavity 4.5 202.29 0 1

Carduelis chloris 1.45 open 5 170.45 0 2 31.7 b

Rhodopechys obsoletus 1.41 open 5 205.43 2 2

Rhodopechys sanguineus 1.59 open 4.5 185.44 0 2

Carduelis flavirostris 1.2 open 5 135.98 1 2

Carduelis cannabina 1.26 open 5 145.36 2 2 41.3 b

Serinus syriacus 1.08 open 4 175.53 0 2

Serinus serinus 1.08 open 3.5 178.42 0 2 24.9

Serinus canaria 1.18 open 3.5 169.7 0 2

Carduelis citrinella 1.08 open 4.5 169.82 0 2

Carduelis carduelis 1.18 open 5 170.92 2 2 75.0

Carduelis flammea 1.11 open 4.5 175.44 0 2

Loxia curvirostra 1.62 open 3.5 138.98 0 2

Loxia leucoptera 1.49 open 4 149.37 2 2

29 a Handbook of the Birds of the World Alive (Del Hoyo et al. 2017, Lynx Edicions, Barcelona, Spain). 30 b Martin, T.E. and Clobert, J. 1996. Am. Nat. 147:1028‐1046. 31 c Wesołowski, T., and Tomiałojć, L. 2005. J. Avian Biol. 36:361‐367. 32 d Akatsuka, T. 2005. Strix 23:51‐58. 33 e Erdös, S. 2008. Ornis Hung. 15‐16:1‐6. 34 f Praus, L. and Weidinger, K. 2015. Acta Ornithol. 50:59‐68. 35 g Praus, L., Hegemann, A., Tieleman, I., and Weidinger, K. 2014. Ardea 102:87‐94. 36 h Shkedy, Y. and Safriel, U.N. 1992. Ibis 134:268‐272.

37 i Taillandier, J. 1993. Alauda 61:39‐51. 38 j Johnsson, K. 1994. Ibis 136:313‐317. 39 l Pearson, S.F., Moore, R., and Knapp, S.M. 2012. J. Field Ornithol. 83:315‐322. 40 n Rodríguez, F., and Moreno, A.C. 2008. Acta Ornithol. 43:207‐215. 41 o Meilvang, D., Moksnes, A., and Roskaft, E. 1997. J. Avian Biol. 28:331‐337. 42

43 Table S2. Relationship between the three variables used to describe juvenile plumage whiteness.

Dependent variable Predictor Post. mean (Post. mean) 95% CI z-score 95% CI Effective sample size pMCMC

Juv. tail whiteness (Intercept) -1.03 -2.08 to 0.02 0.95 to 1.26 3162.74 0.061

Juv. wing whiteness 1.03 0.45 to 1.60 0.95 to 1.25 2057.94 < 0.001

Juv. ventral whiteness (Intercept) 161.86 113.67 to 210.10 1.01 to 1.34 4727.40 < 0.001

Juv. tail whiteness 2.20 -7.39 to 11.70 0.88 to 1.17 4558.40 0.65

(Intercept) 159.68 112.73 to 206.98 0.92 to 1.22 4686.42 < 0.001

Juv. wing whiteness 7.97 -1.19 to 17.09 1.90 to 2.51 4568.74 0.090

45 Table S3. Relationship between adult female whiteness and mean clutch size while controlling for body mass and nest type (open vs. cavity/domed nest)

Dependent variable Predictor Post. mean (Post. mean) 95% CI z-score 95% CI Effective sample size pMCMC

Female tail/wing whiteness (Intercept) -0.14 -2.29 to 2.03 0.79 to 1.05 2366.21 0.90

Clutch size 0.28 0.07 to 0.50 0.87 to 1.15 2380.72 0.009

Nest type (open) -0.25 -0.84 to 0.34 0.89 to 1.18 2341.22 0.42

Body mass -0.34 -1.24 to 0.56 0.91 to 1.21 2350.31 0.46

Female ventral whiteness (Intercept) 203.45 143.29 to 263.33 0.87 to 1.15 3699.58 < 0.001

Clutch size 5.66 1.24 to 10.13 0.85 to 1.13 3684.51 0.013

Nest type (open) -13.04 -24.76 to -1.34 0.84 to 1.11 3676.35 0.031

Body mass -45.27 -66.28 to -24.09 0.88 to 1.16 3689.77 < 0.001

47 Table S4. Relationship between juvenile whiteness and mean clutch size while controlling for female whiteness, body mass, nest type (open vs. 48 cavity/domed nest) and predation rate (data available for 79 species). We show average values of 100 MCMCglmm models ran on 100 random phylogenetic 49 trees. Significant effects (pMCMC < 0.05) are shown in bold. Dependent variable Predictor Post. mean (Post. mean) 95% CI z-score 95% CI Effective sample size pMCMC

Juv. tail/wing whiteness (Intercept) -5.68 -9.43 to -1.94 0.84 to 1.11 2188.39 < 0.001

Clutch size 0.45 0.05 to 0.86 0.95 to 1.26 2238.64 0.029

Female tail/wing whiteness 2.02 1.30 to 2.75 0.81 to 1.08 1917.94 < 0.001

Nest type (open) -1.27 -2.47 to -0.08 0.92 to 1.22 2229.75 0.036

Body mass 1.69 0.02 to 3.38 0.84 to 1.11 2273.59 0.048

Predation rate 0.001 -0.02 to 0.02 0.98 to 1.30 2317.30 0.96

Juv. ventral whiteness (Intercept) 57.94 12.27 to 103.53 1.52 to 2.02 3869.38 0.015

Clutch size -1.10 -4.64 to 2.42 1.09 to 1.45 4679.83 0.539

Female ventral whiteness 0.79 0.68 to 0.91 1.33 to 1.76 3889.68 < 0.001

Nest type (open) -5.37 -15.33 to 4.59 1.54 to 2.03 3170.99 0.294

Body mass -5.91 -24.27 to 12.59 1.68 to 2.22 3560.22 0.517

Predation rate -0.09 -0.28 to 0.11 1.15 to 1.52 4362.37 0.371

51 21

52 Table S5. Relationship between juvenile tail/wing whiteness and mean clutch size while controlling for female tail/wing whiteness, body mass and nest type 53 (open vs. cavity/domed nests), for the whole data set (n = 210 species). We show average values of 100 MCMCglmm models ran on 100 random 54 phylogenetic trees. Significant effects (pMCMC < 0.05) are shown in bold.

Dependent variable Predictor Post. mean (Post. mean) 95% CI z-score 95% CI Effective sample size pMCMC

Juv. tail/wing whiteness (Intercept) -3.61 -5.97 to -1.23 0.98 to 1.30 2353.66 0.003

Clutch size 0.25 0.02 to 0.49 0.92 to 1.21 2321.38 0.034

Female tail/wing whiteness 1.71 1.33 to 2.09 0.96 to 1.27 2110.99 < 0.001

Nest type (open) -0.32 -0.98 to 0.32 0.85 to 1.12 2302.16 0.33

Body mass 0.68 -0.30 to 1.66 0.78 to 1.03 2333.96 0.17

Juv. ventral whiteness (Intercept) 43.27 16.18 to 71.68 1.40 to 1.85 1729.45 0.002

Clutch size -0.88 -2.91 to 1.14 1.15 to 1.52 4080.54 0.397

Female ventral whiteness 0.82 0.75 to 0.89 1.36 to 1.80 1333.99 < 0.001

Nest type (open) -2.33 -7.83 to 3.25 1.04 to 1.38 4609.34 0.409

Body mass -4.70 -14.58 to 4.85 1.19 to 1.58 2541.30 0.352

56 Table S6. Relationship between juvenile whiteness and the two sources of intra‐family conflict explored: clutch size and number of broods (one or more 57 than one per year), which were available for 201 species. The effects of body mass and nest type are controlled for. We show average values of 100 58 MCMCglmm models ran on 100 random phylogenetic trees. Significant effects (pMCMC < 0.05) are shown in bold. Dependent variable Predictor Post. mean (Post. mean) 95% CI z-score 95% CI Effective sample size pMCMC

Juv. tail/wing whiteness (Intercept) -1.27 -3.79 to 1.26 0.99 to 1.31 3573.68 0.33

Clutch size 0.35 0.12 to 0.58 0.87 to 1.15 3239.28 0.003

No. broods -0.32 -0.88 to 0.24 1.00 to 1.33 3407.95 0.27

Nest type (open) -0.27 -0.91 to 0.37 0.78 to 1.03 3378.01 0.41

Body mass 0.22 -0.74 to 1.19 0.92 to 1.21 3489.56 0.66

Juv. ventral whiteness (Intercept) 213.54 159.58 to 268.07 1.01 to 1.34 1086.21 0.001

Clutch size 3.44 -0.79 to 7.68 0.96 to 1.27 1109.08 0.12

No. broods 1.20 -8.19 to 10.49 0.92 to 1.21 1095.26 0.81

Nest type (open) -11.04 -22.58 to 0.45 0.97 to 1.28 1081.72 0.066

Body mass -44.13 -64.47 to -23.97 1.02 to 1.35 110.54 0.001

60 Table S7. Relationship between juvenile tail/wing whiteness and mean clutch size, excluding eleven species in which juveniles are mostly black1 (and, thus,

61 offspring can be conspicuous despite not showing white plumage) and three species in which they show spotted white plumage, which could play a role in

62 camouflage2. The effects of body mass and nest type (open vs. cavity/domed nest) are controlled for. We show average values of 100 MCMCglmm models

63 ran on 100 random phylogenetic trees. Significant effects (pMCMC < 0.05) are shown in bold.

Predictor Post. mean (Post. mean) 95% CI z-score 95% CI Effective sample size pMCMC

(Intercept) -3.34 -5.65 to -1.05 0.91 to 1.21 3440.78 0.005

Clutch size 0.37 0.14 to 0.60 0.85 to 1.28 3272.58 0.002

Nest type (open) -0.10 -0.75 to 0.56 0.79 to 1.05 3417.72 0.78

Body mass 1.39 0.31 to 2.46 0.88 to 1.16 3429.88 0.012

65 1 Species in which juveniles are mostly black: Pyrrhocorax pyrrhocorax, Pyrrhocorax graculus, Corvus rhipidurus, Corvus monedula, Corvus corone, Corvus 66 ruficollis, Corvus frugilegus, Corvus corax, Onychognathus tristramii, Turdus merula and Emberiza cineracea.

67 2 Species in which juveniles show spotted white plumage: Galerida theklae, Irania gutturalis and Saxicola rubetra.