Page 3 - Soldatini_etal2015

Conservation Physiology • Volume 3 2015
are chronically stressed and whether they show any dysfunc-
tion of the HPA axis, in an attempt to apply a physiological
approach to conservation biology, following the suggestions
of Cyr and Romero (2009).
Given that this species has one single-egg brood per year,
the costs of interrupting breeding activity are very high, and
nest abandonment would have serious consequences for the
breeding population. Given the extremely high value of the
single clutch, we hypothesized that birds should show habitu-
ation or show low sensitivity to moderate anthropogenic
stress, such as boat traffic. To test this hypothesis, we com-
pared two groups of birds, i.e. exposed or not exposed to
human disturbance. Besides the classical stress response to
handling stress, following Wingfield et al. (1998), we also con- ried out under permission from the Marine Protected Area no.
ducted a ‘population stress response’, in which we sampled
different individuals of the same group every 5 min over a
period of 40 min. In this way, we obtained the stress response
of a population to human disturbance. Furthermore, we con-
ducted both ACTH and DEX challenge tests, following Cyr
and Romero (2009), to investigate whether the birds were
chronically stressed because of the boat traffic or showed
signs of habituation or reduced sensitivity.
Our results suggest that breeding storm petrels are not
chronically stressed by a mild stressor, such as boat visits, or ming, then climbed up to the nest sites of the outer or inner
alternatively, that there exist individuals within the species
that show a reduced sensitivity to this stressor and can there-
fore breed in tourist-exposed areas without showing physio-
logical signs of chronic stress. However, our data indicate that then moved to the inner chamber, from where noise produced
this type of adaptation might also have negative consequences,
because any further stressors might elicit in an habituated/less ferent nest clusters in order to reduce disturbance to a mini-
sensitive bird an even stronger stress response, with possible
dramatic consequences.
Materials and methods
Study site and species
We studied a colony of ∼2500 breeding pairs of the
Mediterranean subspecies of the European storm petrel on
Marettimo Island, Italy (37°58′20″N, 12°3′20″E; Albores-
Barajas et al., 2012). The study population is composed of
two main sub-colonies: a small (about 150 nests) outer col-
ony, more exposed to external disturbances, and a larger
colony in the inner part of the cave. The outer chamber of the
cave has open access to the sea and is exposed to human dis-
turbance, i.e. noise from boats accessing the entrance of the
cave during the tourist season, which coincides with the
breeding season. The second (inner) chamber is further inside,
and no noise can be heard from there; furthermore, it is more
difficult to access and can thus be considered free from
human disturbance. This provides an excellent model to com-
pare stress responses between ‘human-disturbed’ and ‘non-
disturbed’ breeding sub-colonies. Storm petrels lay single-egg
clutches asynchronously, starting in May–June. Most hatch-
ing occurs during the first half of July; our fieldwork was
conducted during the brooding period. The breeding season
Research article
coincides with the tourist season on the island, when caves Downloaded from http://conphys.oxfordjournals.org/ by guest on March 12, 2016
are visited daily by boats. Tourists are not allowed to land,
but the outer part of the colony is nevertheless exposed to
noise from boat engines and voices, with an average of 10–15
boats approaching the entrance on days with calm seas, while
the inner sub-colony is completely silent and not exposed to
any disturbance.
Both sub-colonies have been visited for ringing every summer
since 1991, while breeding success and parental behaviour have
been monitored more intensely since 2007 (Albores-Barajas
et al., 2015) with 1 month of fieldwork in July every year. Birds
caught during the present study where ringed in previous years,
so they were not handled for the first time. Fieldwork was car-
3/2011 and 1721/2012, and Regione Siciliana.
Experimental procedure
Experiments were carried out during two field seasons in June
2011 and 2012, when most breeding pairs were brooding.
Field work always started at ∼10.00 h and was carried out
only in conditions of good weather, with no relevant differ-
ences in environmental conditions between the 2 years. We
approached the cave by rowing a small rubber boat or swim-
chamber of the cave, avoiding any kind of noise. This
approach usually took 5 min, and we started sampling imme-
diately afterwards. We sampled the outer chamber first and
in the outer one cannot be heard. Every time, we sampled dif-
mum. In the outer chamber there are three nest clusters
separated by rock walls, and in the inner chamber there are
four nest clusters on different terraces, allowing us to work at
the lower level while leaving the upper ones undisturbed.
We quantified the physiological stress response of adult
storm petrels by measuring the plasma levels of CORT (see
‘Radioimmunoassay procedure and biochemical validations’
below). Blood samples (∼100 μl) were collected from the wing
vein with heparinized capillaries and centrifuged. The plasma
was separated and kept on ice until returning to the station,
and then stored at −20°C. After obtaining the blood sample,
we measured wing length, tarsal length, bill depth and width
and head size in order to estimate body condition.
Experiments
Experiment 1: individual stress response
During the breeding seasons 2011 and 2012, we compared
the stress response between disturbed and non-disturbed
groups (n = 4 from each group in 2011; and n= 10 non-dis-
turbed and n = 11 disturbed in 2012). A baseline blood sam-
ple was collected within 5 min of entering the cave chamber.
Thus, in 2011 only one bird per colony was sampled each day
on our arrival and then after 30 min, while in 2012 using the
same procedure, we used the control and saline-injected
groups of experiment 3 (for more details see ‘Experiment 3:
3