930 F. Zino et al.


TABLE 1 The numbers of recorded nest sites and chicks of Cory’s shearwater Calonectris borealis fledged and the per cent of recorded nests sites with fledged chicks for the two quadrats (ABCD, EFGH) on the island of Selvagem Grande (Fig. 1) for 1982–2020. Breeding attempts may not have occurred at some nest sites (see text for further details).


ABCD Year


Number of nest sites recorded


Before mammal eradication 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1996 1998 1999 2001


170 188 200 203 203 203 216 227 214 213 229 215 219 211


Mean ± SD 207.93 ± 15.41 208


After mammal eradication 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020


206 208 232 234 241 249 251 250 269 261 279 290 296 312 316 317 324 329


Mean ± SD 266.95 ± 40.90


Number of fledged chicks


59 56 81 68 88 80 96 78 96 82 75 70 75 75


130 93


150 101 123 131 134 122 124 143 125 129 159 157 196 186 179 178


% nest sites with fledged chick


34.71 29.79 40.50 33.50 43.35 39.41 44.44 34.36 44.86 38.50 32.75 32.56 34.25 35.55


77.07 ± 11.77 37.04 ± 4.82 110


52.88 63.11 44.71 64.66 43.16 51.04 52.61 53.39 48.80 46.10 54.79 44.80 44.48 53.72 50.32 62.03 58.68 55.25 54.10


140.53 ± 28.90 52.56 ± 6.41


were not uniform between the two quadrats. In their prelim- inary study, Zino et al. (2008) found that fledging prior to eradication in quadrat ABCD was lower than in quadrat EFGH. After eradication, fledging rates in both quadrats in- creased but the increase was greater in ABCD, so that fledg- ing rates were similar in the two quadrats. These effectswere again found in the larger data set that we present here. Mean annual fledging rate (fledglings per 100 nest sites) in quadrat EFGH prior to the removal of the mammals was, as given above, 45.3 ± 5.0 (n = 14), whereas in ABCD the rate was 37.0 ± 4.8 (n = 14). These means are significantly different (t = 2.23,df = 26,P= 0.017). However, fledging


EFGH


Number of nest sites recorded


134 145 156 156 154 171 175 180 188 185 206 193 197 192


173.71 ± 21.64 200


189 189 207 202 213 199 217 225 229 212 235 177 225 261 265 268 276 278


224.58 ± 31.35


Number of fledged chicks


68 57 74 82 80 87 76 87 84 79 81 78 85 75


78.07 ± 8.07 99


115 108 123 104 113 124 106 110 118 115 103 93


125 136 157 146 139 134


% nest sites with fledged chick


50.75 39.31 47.44 52.56 51.95 50.88 43.43 48.33 44.68 42.70 39.32 40.41 43.15 39.06


45.28 ± 4.97 49.50


60.85 57.14 59.42 51.49 53.05 62.31 48.85 48.89 51.53 54.25 43.83 52.54 55.56 52.11 59.25 54.48 50.36 48.20


119.37 ± 16.93 53.35 ± 4.83


rates after the eradication, 52.6 ± 6.4 (n = 19) and 53.4 ± 4.8 (n = 19) in quadrats ABCD and EFGH, respectively, did not differ significantly (t = 0.45,df = 34,P = 0.329). This in- dicated that recovery of shearwater breeding after eradica- tion was more marked in quadrat ABCD than in EFGH. Others who have studied breeding of Cory’s shearwater


on Selvagem Grande have estimated nest failure during the breeding season (Mougin et al., 1996; Granadeiro et al., 2006). From 2009, when the regularity of our visits increased, we were able to assess numbers of breeding at- tempts made by birds nesting in the quadrats. A breeding attempt was defined as the laying of an egg, irrespective of


Oryx, 2022, 56(6), 927–934 © The Author(s), 2021. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605321000661


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108  |  Page 109  |  Page 110  |  Page 111  |  Page 112  |  Page 113  |  Page 114  |  Page 115  |  Page 116  |  Page 117  |  Page 118  |  Page 119  |  Page 120  |  Page 121  |  Page 122  |  Page 123  |  Page 124  |  Page 125  |  Page 126  |  Page 127  |  Page 128  |  Page 129  |  Page 130  |  Page 131  |  Page 132  |  Page 133  |  Page 134  |  Page 135  |  Page 136  |  Page 137  |  Page 138  |  Page 139  |  Page 140  |  Page 141  |  Page 142  |  Page 143  |  Page 144  |  Page 145  |  Page 146  |  Page 147  |  Page 148  |  Page 149  |  Page 150  |  Page 151  |  Page 152  |  Page 153  |  Page 154  |  Page 155  |  Page 156  |  Page 157  |  Page 158  |  Page 159  |  Page 160  |  Page 161  |  Page 162  |  Page 163  |  Page 164