Breeding in an agricultural landscape 243


et al., 2006) date of hatching (Mayfield, 1975; Kubelka et al., 2018). For predated nests, we calculated exposure from the day of nest finding until the midpoint between the last positive and the first negative visit to the nest. For all other outcomes (i.e. unknown, abandoned, flooded, de- stroyed by agricultural machinery), we defined exposure time from the day of nest finding until the last positive nest visit, following standard protocols (Kubelka et al., 2018). We focused trail cameras on 116 nests to identify species of nest predators and the date of hatching.


Statistical analyses


PLATE 2 Protection zone around collared pratincole nest, marked temporarily by 1.5 m-tall wooden poles. This photograph was taken using a telephoto lens that distorts the actual distance between the two wooden poles.


The survival and productivity of ground-nesting birds


are influenced by predation (Martin, 1993; Roodbergen et al., 2012; Kubelka et al., 2018). To investigate relation- ships between pratincole breeding success and number of nest predators removed from the study area, we collected data from hunters. Potential huntable nest predators include mammals (red fox Vulpes vulpes, golden jackal Canis aur- eus, European badger Meles meles) and birds (Eurasian magpie Pica pica, hooded crow Corvus cornix). We re- quested hunting bag data from professional hunters for the period 2017–2021 and we aggregated the number of individuals killed for each year. Hunting bag data relate to the regional hunting district (c. 26,000 ha), which covers c. 65% of collard pratincole nest sites (National Game Management Database, 2022).


Estimating daily and total nest survival


To investigate the effects of year and agricultural habitat on nesting success, we estimated daily and total nest survival rates using calculations provided by Mayfield (1975). We applied this method to estimate the chances of a clutch surviving daily and for the full nesting period (egg laying + incubation period) by defining the daily nest survival rate as the number of failed nests divided by the sum of exposure days (Johnson, 1979). We calculated total nest survival using Mayfield’s formula: (daily nest survival)nesting period in days, where the total nesting period is egg laying period + incubation (20 days in total). We defined exposure time as the number of days from find- ing a nest to the confirmed (or expected) last day of the breeding attempt. The incubation period started when the complete clutch had been laid. For those nests that hatched (i.e. at least one chick hatched), we calculated the exposure time from the day of nest finding to the confirmed (or predicted, using the egg floating methodology; Székely


We performed the statistical analyses in R 3.3.3 (R Core Team, 2021). To identify relationships amongst individual- level reproduction success metrics (i.e. nests hatched or failed and the number of hatched chicks), we used general- ized linear models (GLMs) with factors of year, habitat type, Julian day of egg laying, distance from the closest field boundary, distance from the closest water body and colony density. The latter factor represented the mean distance from the focal nest to the three closest nests within the same breeding colony. As nesting success was a binary response variable (hatched or failed), we used a logistic regression GLM with the logit link error function. Field boundaries and water bodies were available in shape files. We computed the mean distance from the three neighbouring nests using the nndist spatial neighbour- hood function available in the spatstat package in R.For the start of incubation, we used the Julian day of clutch completion at a given nest. We used ANOVA, imple- mented using the lm function, to analyse the associations between (1) clutch size and habitat type, (2) timing of hatching and habitat type, and (3)daily nest survival (aggregated for years and habitats).


Results


Timing of breeding and breeding success During 2012–2021, we found 315 nests, for 212 of which we also determined the hatching date of the first chick. Egg laying started in late April and terminated in mid July (c. 2.5 months duration), with most nests (60%) laid dur- ing 25 May–15 June. The first eggs hatched on 16 May, which implies that the clutch was completed on 29 April. The latest hatch date was recorded on 3 August. The mean hatching date was 15 June ± SE 1 day (n = 212 nests; Table 1, Supplementary Fig. 1). Collared pratincoles bred in three agricultural habitats:


most nests were in row crops (48%), followed by fallow lands (29%) and spring cover crops (23%, n = 315 nests; Table 1). The timing of breeding was different between


Oryx, 2024, 58(2), 240–249 © The Author(s), 2023. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605323000911


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