Baylis et al. • CAPSAICIN AS A NEST PREDATION DETERRENT 
519 
poultry feed from mice and ruts (Jensen et ul. 2003), 
as mammals are deterred by the application of 
capsaicin to items they would otherwise consume. 
We consider from a cognitive perspective that 
capsaicin treatment may cause predation deterrence 
on focal avian nests in two ways. First, capsaicin 
treatment may result in behavioral responses from 
direct trigeminal irritation (Clark 19%). Second, 
once predators have been exposed to capsaicin, it 
may deter further predation attempts as a learned 
aversion (Kimball et al. 2009). Deterrence, in the 
case of a learned av ersion, may not be specific to 
capsaicin-treated eggs and may generalize to items 
that resemble the olfactory, tactile, and/or visual 
cues of those treated with capsaicin. 
We investigated the possibility of applying 
capsaicin as a selective avian nest-predation 
deterrent against invasive mammals in N'ew 
Zealand using artificial nests. We predicted nests 
treated with capsaicin-containing chili powder 
would be less appealing to mammalian predators 
than untreated nests, or treated with non-pungent 
paprika. We also investigated the effect of 
attaching chili powder to eggs using an adhesive 
to see if this would be necessary to prevent 
weather-related loss of chili powder over time 
tinder field conditions. 
METHODS 
Study Area .—Our study area was the New' 
Zealand Bush section of the Auckland Regional 
Botanic Gardens (ARBG) in Auckland, New 
Zealand (37 00' S, 174 54' E). The New Zealand 
Bush of ARBG covers 1.48 ha in a narrow, I-km 
long strip. The ARBG is in a suburban area, 
surrounded to the east and south by housing, to the 
west by motorways and on- and off-ramps, and to 
'he north by Totara Park, a 216-ha area of mixed 
hush and open grassland. Rat control through 
poisoned bait stations is undertaken by commercial 
contractors in Totara Park, but not within ARBG. 
Field Procedures.—We constructed imitation 
(artificial) nests (// = 60) resembling those of 
European thrushes (Turdus spp.) and placed them 
"i the ARBG during the 2009-2010 austral 
s ummer. We used imitation thrush nests because, 
in areas without poison control of mammals, 
introduced Turdus spp. are the most common nest 
c up-nesting wild birds; most New Zealand native 
and endemic bird species arc also cup nesters 
(Marchant et al. 1990-2002). Imitation nests each 
contained three eggs: two imitations, and one real 
egg of King Quail (Excalfactoria chinensis). 
acquired from a local breeder as unincubated 
(freshly laid) eggs and stored at 4 C prior to use. 
Each nest contained eggs of only one experimen¬ 
tal treatment type. 
Imitation Nests and Eggs .—We constructed 
imitation nests by hand. Nests consisted of a dar¬ 
kened (painted dark-brown using a mix of Fas 
Student Acrylic black, brown, and sap green) 
cardboard base formed into a shallow cone (radius 
= 80 mm; depth = 50 mm) (Fig. I). These were 
stuffed with dried, autoclaved lawn clippings just 
prior to placement. We primarily anchored nests into 
trees by wedging them between branches in the same 
manner as real Turdus spp. nests in New' Zealand 
(Igic et al. 2009); each nest was also attached to the 
tree by a tie-wire incorporated into its base structure. 
The tie-wire served the dual purpose of stabilizing 
nests, and preventing them from being removed by 
larger nest predators or extreme weather. 
We cast imitation eggs (length = 23.7 mm; 
width = 18.8 mm; mass = 4.94 g) in plaster-of- 
Paris from moulds taken from real eggs of captive 
King Quail. All imitation eggs were constructed 
with a length of string protruding from their sides 
(following Boulton and Cassey 2006) so they 
could be tied to the nest structure to prevent 
removal by predators (Fig. 1). We painted imita- 
tion eggs using water-based paints (mixed from 
Golden fluid acrylics™ in Raw Umber, Raw 
Sienna, Phthalo Green. Primary Cyan, and Titan 
Buff colors) to visually match Turdus spp. eggs as 
judged by a mammalian (human) eye. We also 
painted the real quail eggs used in the same 
manner to avoid influencing predation patterns 
with a paint effect. 
Treatments.—We manipulated eggs with one of 
five treatments: untreated, powder chili, powder 
paprika, adhesive chili, and adhesive paprika. 
Paprika served as a conspecific plant control for 
capsaicin-containing chili powder (Heiser and 
Smith 1953). Paprika is derived from cultivars 
of C. annum with either no capsaicin (Ayuso et al. 
2007), or only low levels of capsaicin (Peusch 
et al. 1996) in their fruit and. at most, is only 
mildly pungent (Peusch el al. 1996). We tested the 
paprika used in our experiment for pungency 
using the oral test of Seovillc (described in 
Szallasi and Blumberg 1999), and found it not 
to be ‘hot’-tasting, even undiluted. Thus, paprika 
served as a control for the visual and tactile 
stimuli provided by chili powder relative to the 
capsaicin content itself. We acquired both paprika 
and chili commercially in local food stores. 
