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Supplementary material
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3
Supplementary experiments
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Experiment S1. Experiment to identify main egg predators and sensory cues used to
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detect nests
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A key assumption of this study was that little ravens, a visually foraging daytime
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predator of red-capped plover eggs, were the primary diurnal egg predator at the sites.
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Remote sensor cameras were deployed 2-3 m from 42 uncovered bait stations set up
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with or without two quail eggs each and each bait station was systematically assigned
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to one of three treatments after randomly assigning the first nest to a treatment (14
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stations in each treatment). Treatments were: i) ‘scent cues only’ in which two quail
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eggs were placed inside a perforated plastic container and the container was
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completely buried so that scent could escape, ii) ‘visual and scent cues’ where the two
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quail eggs were placed on top of the buried perforated container, and iii) ‘control’ where
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only the perforated plastic container was buried without eggs. Bait stations were
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placed at least 200 m apart (235.7 ± 4.1 m; 201.0 – 302.0 m) on a 10.4 km transect
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along the coast at the Western Treatment Plant (37o 59’ S, 144o 35’ E; ~11,000 ha) in
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Werribee, west of Melbourne in Victoria, Australia. Specific sites were chosen because
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they matched potential red-capped plover breeding locations, and were suitable for
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installation of a false nest. Cameras were deployed for a period of four weeks to mimic
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an incubation period and images were examined for differences in rates of detection
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of eggs by predators during daytime and night.
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The main predators responsible for preying on quail eggs were little raven and red fox
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(53% and 47% of all depredation events respectively; n = 15). Ten out of 15 (66%)
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predation events occurred during the daytime. Little ravens accounted for eight of ten
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depredated events at experimental nests during daytime (see Table S1). They
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occurred only during daytime, and only detected nests offering a visual cue (Fisher’s
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Exact Test; p = 0.001), confirming that they are a visually foraging daytime predator of
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eggs. On the other hand, there was no difference in the occurrence of foxes during
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daytime and night and they were attracted to both ‘scent cues only’ and ‘visual and
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scent cues’ treatments (Fisher’s Exact Test; p = 0.19). This suggests foxes use scent
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and possibly visual cues to detect eggs during night and daytime.
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Table S1. The number of predators lured to three treatments (‘control’, ‘scent cues
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only’ and ‘visual and scent cues’), each with 14 bait stations in the predator presence
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and sensory cue experiment.
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Occurrence during
Occurrence during
daytime
night
Fox
0
0
Little raven
0
0
Fox
1
4
Little raven
0
0
Fox
1
1
Little raven
8
0
Treatment
Predator
Control
Scent cues only
Visual and scent
cues
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2
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Supplementary tables
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Table S2, related to Figure 3. Model selection results for the probability of clutch
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depredation for the red capped plover (df = degrees of freedom; logLik = log likelihood;
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AICc = AIC values adjusted for small samples; ∆i = Delta AICc; wi = model weight; D2
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= test statistic).
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Model
df
logLik
AICc
∆i
wi
D2
Sex * Time
4
-191.47
391.05
0.00
0.53
26.58
Sex * Time + Water
5
-191.39
392.93
1.88
0.20
26.61
Sex * Time + Vegetation
5
-191.46
393.07
2.02
0.19
26.58
Sex * Time + Vegetation + Water
6
-191.33
394.87
3.82
0.08
26.63
Sex + Time
3
-215.70
437.46
46.41
0.00
17.29
Sex + Time + Water
4
-215.64
439.38
48.33
0.00
17.31
Sex + Time + Vegetation
4
-215.69
439.47
48.42
0.00
17.29
Sex + Time + Vegetation + Water
5
-215.60
441.35
50.30
0.00
17.33
Sex
2
-229.00
462.02
70.97
0.00
12.19
Sex + Water
3
-228.95
463.95
72.91
0.00
12.21
Sex + Vegetation
3
-228.99
464.04
72.99
0.00
12.19
Sex + Vegetation + Water
4
-228.92
465.94
74.89
0.00
12.22
Time
2
-249.62
503.28
112.23
0.00
4.28
Time + Water
3
-249.19
504.44
113.40
0.00
4.45
Time + Vegetation
3
-249.25
504.57
113.52
0.00
4.42
Time + Vegetation + Water
4
-249.03
506.16
115.11
0.00
4.51
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3