Nest protection for threatened birds 95


TABLE 3 Set of candidate ideas for nest protection developed during the expert elicitation, based on the list of interventions developed during the pre-expert elicitation (Table 2). Ideas sought to mitigate the risk of nest failure from avian predation, mammalian predation, extreme weather events and competition.


Action


Avian predation Nest cages


Lethal control Acoustic control


Mammalian predation Olfactory/acoustic camouflage


Acoustic control


Double-sided sticky tape Tree collars


Description


Construct cage (green plastic trellis) over 1 to several days, designed to allow access for regent honeyeaters but not for avian predators


Shooting, trapping & translocation of a subset of species (e.g. ravens Corvus corax, kooka- burras Dacelo novaeguineae, pied currawong Strepera graculina, grey butcherbirds Cracticus torquatus), from egg-laying through to fledging


Broadcast alarm calls (not immediately adjacent to nest); would need to be refined


Use the scent of prey to disincentivize predators, by incorporating scent of prey in petroleum jelly smeared on trees. Predators that cue in on scent to find prey will be disincentivized from associating the smell with a food reward, and will switch prey temporarily. A similar concept could be applied to acoustic camouflage.


Broadcast synthetic ultrasonic signals and/or miscellaneous high frequency vocalizations from gliders/possums to elicit territorial avoidance


Similar to fly traps, but wrapped around a tree or branch to deter gliders (e.g. sugar and squirrel gliders)


Various designs could be trialled (e.g. funnel/Elizabethan collar), on tree trunk or on the primary branches, where nests are built


Hold non-threatened arboreal mammals Trapping & housing family groups in proximity to nest location or hold in zoo enclosures until regent honeyeater fledge their young, and then release at site of origin


Cull non-threatened arboreal mammals Trap & kill (up to 10 individuals in close proximity to a nest) Move non-threatened arboreal mammals away


Extreme weather events Supplementary food resources Fire & fuel management Landscape management


Competition Noisy miner control


Squirrel gliders seem to be attracted to light: use lights to attract them elsewhere, or artificial nectar to sate/attract squirrel gliders


Provide food & water, & potentially nesting material, after severe storms & during droughts Prioritize fuel reduction in areas of high-quality nesting habitat Habitat recovery/restoration measures after droughts & fire events


Shooting before breeding season (proactively)&fromtime of regent honeyeater egg-laying to fledging (reactively)


Most of the candidate ideas rely on detecting nests prior


to local deployment. The results in Fig. 2 report the success rate conditional on detecting nests at or before the time of eggs being laid. This is equivalent to nest detection Scenario 1 in Table 5. Three other scenarios of imperfect detectability of nests are included in Table 5. Scenarios 3 and 4 appear to be broadly consistent with detection in recent years (D. Ingwersen, pers. comm, 2022). In Table 6 the estimated implications of imperfect nest


detection for the recruitment of juveniles are reported. Where the best (or near-best) four ideas (for each of avian predation, mammalian predation, extreme weather events and competition) are deployed simultaneously, the esti- mated recruitment rates for wild birds are 1.35 and 1.15 juve- niles per female per breeding season for Scenarios 3 and 4, respectively (see calculations in Supplementary Materials 1 & 2). Experts were asked for judgements of the effectiveness of protection measures one at a time. To obtain the aggre- gate effect of deploying multiple measures, calculations as- sume independence, such that the effectiveness of any one protection measure is unaffected by the effectiveness of a


second, third or fourth measure. For released birds, the rates for Scenarios 3 and 4 are 1.13 and 0.90 juveniles, respectively. The recruitment rates (Table 6) use best estimates for


nest success in the calculation of the proportion of success- ful nests and the recruitment rate. Using the upper bounds of the 90% credible intervals for nest success (Fig. 2), the recruitment rates for Scenarios 3 and 4, for both wild and released birds, are c. 1.4 and 1.7 juveniles per female per season, respectively. Therefore, with a parallel investment in improving nest detection, it is possible that nest pro- tection can provide a pathway for recovery of the regent honeyeater. Additionally, future nest surveys could usefully include the stage of detection (pre egg-laying, egg to hatching and hatching to fledging) to provide an im- proved empirical basis for the nest detection scenarios (Table 5) and the recruitment rates (Table 6). The analyses presented here do not consider all possible


ideas. Other ideas that were excluded from the elicitation include: (1) visual and acoustic control of mammalian predators (excluded because the lag time for developing the image display technology was considered too long);


Oryx, 2025, 59(1), 91–100 © The Author(s), 2024. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605324000942


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