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Gulf of Mexico Natural History and Oil Spill Impacts Special Series
Short-Term Response of Brown Pelicans (Pelecanus
occidentalis) to Oil Spill Rehabilitation and Translocation
Will Selman1,*, Thomas J. Hess, Jr.1, Brac Salyers1, and Carrie Salyers1
Abstract - Translocation of wildlife is a valuable tool for managers to alleviate impacts
of human/wildlife conflicts, habitat fragmentation, and small population sizes. Pelecanus
occidentalis (Brown Pelican) were previously successfully translocated into
Louisiana in 1960–1980s and had rebounded significantly prior to the Deepwater Horizon
Oil Spill in April 2010. The Deepwater Horizon Oil Spill had a dramatic impact on southeastern
Louisiana, including the people, wildlife, and coastal habitats of the region. We
translocated 182 oil-rehabilitated Brown Pelicans from southeastern Louisiana to an area
non-impacted by the oil spill in southwestern Louisiana (Rabbit Island, Cameron Parish).
Daily surveys were conducted at the island for six weeks and documented mortality, movements,
integration with local pelican flocks, persistence of pelicans at the island, and the
role of supplemental feeding. We documented no mortality of rehabilitated birds and found
that translocated Brown Pelicans readily integrated with local pelican flocks. Supplemental
feeding likely contributed to the persistence of pelicans at Rabbit Island from weeks 1 to 4.
By weeks 4 to 6, many local and translocated pelicans moved away from the island, likely
due to a combination of natural and human-induced factors. After the initial stages of the
translocation, we tentatively suggest that the program was a success and propose recommendations
for future translocation attempts with Brown Pelicans.
Translocation, or the moving of living organisms from one locality to
another, has been widely used by wildlife managers to supplement wildlife
populations, re-establish populations, or to establish new populations (Armstrong
and Seddon 2008, IUCN 1987). Translocation techniques are becoming
increasingly important with rare, threatened, or endangered species that have
been extirpated from all or part of their native range (Griffith et al. 1989, Kleiman
1989). However, to determine the effectiveness of a wildlife translocation
project, it is critical to quantify the short- and long-term success or failure of
the project. Yet, many projects fail to adequately quantify the success or failure
of a translocation effort and/or document alternate strategies that may have improved
translocation success (Griffith et al. 1989). Consequently, the outcome
of many translocation projects performed in the past remains unknown (Dodd
and Seigel 1991, Fischer and Lindenmayer 2000).
During the 1940s, Pelecanus occidentalis L. (Brown Pelican) were considered
a “common bird” to Louisiana, but their populations were “decreasing
in numbers” (LDWF 1941). By the early 1960s, Brown Pelicans had ceased
1Rockefeller Refuge, Louisiana Department of Wildlife and Fisheries, 5476 Grand
Chenier Highway, Grand Chenier, LA 70643. *Corresponding author - wselman@wlf.
G2 Southeastern Naturalist Vol. 11, No. 1
nesting in Louisiana (Williams and Martin 1968), with environmental pesticide
contamination and subsequent eggshell thinning as a plausible link to declines
(Blus et al. 1979). Following the banning of many toxic pesticides (i.e., endrin,
DDT), translocation efforts were conceived by Louisiana Department of Wildlife
and Fisheries (LDWF) and the Florida Game and Fresh Water Fish Commission
to restore Brown Pelicans to Louisiana (Nesbitt et al. 1978) to recipient sites that
previously had nesting colonies of the species (i.e., barrier islands of southeastern
Louisiana). Between 1968 and 1980, 1276 Brown Pelicans were translocated
from Florida to Louisiana (McNease et al. 1992), and these translocations were
considered extremely successful (Holm et al. 2003, McNease et al. 1992). Prior
to the Deepwater Horizon oil spill off the southeastern coast of Louisiana, these
barrier islands had 9 active Brown Pelican nesting colonies, with approximately
10,114 nesting pairs (Hess and Linscombe 2010). Coastal land loss is a major
concern to existing pelican-nesting barrier islands in southeastern Louisiana
(Holm et al. 2003; S. Walter et al., University of Louisiana-Lafayette, Lafayette,
LA, unpubl. data). Further, many of the barrier islands that held the largest nesting
colonies of Brown Pelicans, and the islands that were the focus of translocation
efforts between the 1960s and 1980s, were some of the most heavily impacted
areas following the Deepwater Horizon Oil Spill (LDWF 2010, NOAA Fisheries
Service 2010). Ironically, the Brown Pelican was removed from the Endangered
Species List by the US Fish and Wildlife Service (USFWS) five months prior to
the Deepwater Horizon Oil Spill, primarily due to the recoveries that have been
achieved in Louisiana and the northern Gulf of Mexico region (USFWS 2009).
The Deepwater Horizon explosion and oil spill was the largest offshore oil
spill in US history, releasing an estimated 4.4 million barrels of oil (7.0 x 105
m3 ± 20%; Crone and Tolstoy 2010) into the Gulf of Mexico. Consequently, this
had a dramatic impact on the coastal habitat/wildlife of southeastern Louisiana
and neighboring Gulf of Mexico states (Restore the Gulf 2010). The response by
local, state, federal, non-profit, and academic entities to the oil spill occurred on
a massive scale, with many performing wildlife surveys, both on and off shore.
During these surveys, many oiled wildlife specimens were found both dead and
alive (i.e., birds, sea turtles, marine mammals; Restore the Gulf 2010). Individuals
that were found alive were taken to wildlife habilitation facilities, with
the ultimate goal of eventually releasing them back into their native habitats.
However, many of these habitats in the southeastern part of the state remained
impacted for prolonged periods (LDWF 2010, NOAA Fisheries Service 2010)
and thus, successfully rehabilitated individuals could not be released back into
their original sites of collection. These heavily impacted areas included many of
the barrier island chains of southeastern Louisiana utilized by Brown Pelicans for
nesting colonies (Hess and Linscombe 2004).
In contrast to southeastern Louisiana, the southwestern part of the state
was relatively unimpacted by the Deepwater Horizon Oil Spill (LDWF 2010,
NOAA Fisheries Service 2010). In southwestern Louisiana, Rabbit Island
serves as the only active nesting colony for Brown Pelicans. In 2003, a small
nesting colony was discovered on Rabbit Island (4 nests, 7 fledglings; Hess
2012 W. Selman, T.J. Hess, Jr., B. Salyers, and C. Salyers G3
and Linscombe 2003), a small shell island in West Calcasieu Lake (≈89 ha [220
acres]; 29º50.882'N, 93º23.014'W). Since the discovery of the Rabbit Island
nesting colony, the local Brown Pelican population has increased substantially,
with approximately 1000 fledglings per year and a local adult population of at
least 3000–5000 individuals (T.J. Hess, Jr., pers. observ.). We determined that
Rabbit Island would make a suitable candidate translocation site for oil-spillrehabilitated
Brown Pelicans for multiple reasons: 1) Rabbit Island is currently
a suitable nesting habitat for local Brown Pelicans, 2) this area was not impacted
by the Deepwater Horizon Oil Spill, 3) the resident Brown Pelican population
continues to increase in size and only utilizes parts of the island for nesting,
4) there are bountiful foraging opportunities in the region (i.e., Calcasieu
Lake and Gulf of Mexico), and 5) prior attempts to translocate Brown Pelicans
in Louisiana have been successful. Further, we also presumed that the native
population would not suffer any ill effects or genetic “swamping” following
supplemental translocations of oil-rehabilitated Brown Pelicans. The latter was
not an issue as almost all of the Louisiana Brown Pelicans are derived from
previously translocated Florida stock from 1968–1980 (McNease et al. 1984,
Nesbitt et al. 1978).
Prior to translocation, we proposed to document the efficacy of the translocation
effort of oil-rehabilitated Brown Pelicans from native southeastern Louisiana
marshes to the existing Rabbit Island colony in southwestern Louisiana. Specifi-
cally, we selected several a priori research questions with which we could gauge
the success/failure of the translocation: 1) would we document any mortality in
translocated birds?, 2) how long would translocated and local Brown Pelicans
remain at Rabbit Island?, 3) would translocated Brown Pelicans integrate into
native pelican groups?, 4) would supplemental feeding of translocated birds
improve retention?, and 5) would we be able to adequately monitor short-term
movements of translocated birds?
Out of the 719 total oil-recovered Brown Pelicans from southeastern Louisiana,
182 Brown Pelicans (166 hatch year, 14 after hatch year, 2 unknown
age) were rehabilitated and translocated to Rabbit Island (Fig. 1); pelicans
were translocated to other states prior to this translocation due to fear of the oil
spill impacting the whole coast of Louisiana. Prior to leaving the rehabilitation
facility, metal bands and colored auxiliary bands (red or pink bands with large
alphanumeric codes) were affixed to the legs of translocated Brown Pelicans.
The birds were transported from the rehabilitation facilities to Cameron, LA
(Cameron Parish) in six different translocation events (Table 1). Pelicans were
transported in an air-conditioned covered trailer and in pet carriers (maximum
2 pelicans per carrier). They were delivered early in the morning to avoid any
heat stress that may have occurred during the middle of the day. Upon arrival in
Cameron, each individual was inspected by a veterinarian to ensure a positive
health status prior to being released by LDWF staff at the northern end of Rabbit
G4 Southeastern Naturalist Vol. 11, No. 1
Figure 1. Recovery locations of 183 oiled Brown Pelicans (grey circles) that were rehabilitated
and translocated to Rabbit Island (inset). Sixty-eight Brown Pelicans were
recovered from Raccoon Island and 67 in the Barataria Bay region.
Table 1. Brown Pelican translocation dates to Rabbit Island (Cameron Parish, LA), number of
pelicans released, and colored leg-band codes.
Translocation # of pelicans
date released Colored-band numbers
5 August 2010 15 Pink (A55–A69)
6 August 2010 59 Pink (A70–A84), Red (0Z5–7Z1, except 4)
20 August 2010 33 Pink (A85–A00; C01–C04, C06–C14), Red (2Z1, 6Z4, 6Z8, 7Z1)
28 August 2010 48 Pink (C05, C15–C61)
3 September 2010 19 Pink (C62–C80)
10 September 2010 8 Pink (C81–C88)
2012 W. Selman, T.J. Hess, Jr., B. Salyers, and C. Salyers G5
Island. We chose the northern end of the island as it had fewer resident pelican
nests, and subsequent hatch-year birds already present, relative to the southern
end of the island.
Rabbit Island counts
Following the initial translocation event (5 and 6 August 2010), we made
daily counts for roosting Brown Pelicans on Rabbit Island for 6 weeks (from
7 August 2010 to 18 September 2010). Thirty-seven daily counts were completed,
and we did not complete surveys on five days due to severe weather or
on days of additional pelican releases. Surveys started at 0715 hrs and lasted
approximately 1.5 hours. During each survey, we counted both auxiliary red/
pink-banded pelicans (hereafter “banded”) and unbanded pelicans from the
deck of a push barge while it moved slowly around the island, approximately
100–150 m from shore. Other band colors were observed (i.e., yellow, green,
white), but these individuals were adults, and therefore, we are confident that
those birds observed with red or pink bands were the part of the translocation
group of pelicans. The island was divided into a northern and southern section,
and pelicans were counted individually using a 20–60x spotting scope (Leica
Televid 77) with tripod and/or 12 x 36-mm image-stabilizing binoculars (Canon).
We also opportunistically took photographs (Nikon D90) of banded birds
in transit between the boat ramp and Rabbit Island, during counts, or during
supplemental feedings (discussed further below). Following the 18 September
survey, we continued weekly monitoring at Rabbit Island and the surrounding
region (i.e., Calcasieu Ship Channel, Cameron Jetties) until 29 October 2010
(6 additional surveys); weekly data will not be used for statistical comparisons
but will be discussed.
Following the first translocation, we provided supplemental feedings of dead
fish to translocated Brown Pelicans. This feeding was done in an attempt to
increase retention rates of translocated birds (i.e., prevent long-distance movements
back toward the oil-spill impacted area) and is similar in concept to other
supplemental feedings in previous translocation events with Brown Pelicans
(Joanen and McNease 1974, Nesbitt et al. 1978). Frozen Brevoortia patronus
Goode (Gulf Menhaden; ≈15–25 cm total length), a locally common fish species
and a staple in Brown Pelican diets (Franklin 2007), were thawed to ambient
temperatures before feeding to pelicans. Following all visual surveys, feeding
was completed by tossing fish into the water from a motorized boat; researchers
opportunistically took photographs of banded pelicans during this time as
they would be feeding near the boat. Supplemental feeding occurred for 31 days
following the initial release of the first pelican group. The schedule for pelican
feeding was twice a day (morning and evening; Joanen and McNease 1974) and
133 kg (500 lb) of menhaden per feeding. During the study, habituation to the
feeding and to the presence of the feeding boat occurred with both translocated
G6 Southeastern Naturalist Vol. 11, No. 1
and local birds. Once it was clear that such habituation was occuring, supplemental
feeding was suspended at the recommendation of the authors. Thus, there
was no supplemental feeding that occurred for the last 9 survey days of the study
(weeks 5 and 6).
Since the number of pelicans counted during the daily counts deviated
from normality, we used a Kruskal-Wallis test to determine if daily counts
were equal across sample weeks. Also, we standardized the number of banded
pelicans observed to percent of banded pelicans observed; this standardization
was done due to the changing number of banded pelicans available in our
population after every release event. Similarly, the daily percentage of banded
pelicans observed was non-normal, and therefore, we used a Kruskal-Wallis
test to calculate if percentages were equal across sample weeks. Lastly, we
used a Kruskal-Wallis test to determine if the number of banded pelicans relative
to the total pelicans observed (in percent) were equal across weeks; this
was done in order to determine if a larger number of the banded pelicans remained
on the island relative to the local pelicans.
To determine the effect of supplemental feeding on the pelicans, we used
a Wilcoxon rank sums test (with chi-squared approximation) to determine if
1) pelican counts and 2) percentage of banded pelicans observed were equal during
and after supplemental feeding.
Throughout our surveys, we did not document any mortality of the 182 translocated
pelicans, but we did notice several fresh carcasses of non-translocated
Brown Pelicans at Rabbit Island. We also did not receive any calls from the public
on Brown Pelican carcasses with bands in the area.
Persistence of pelicans at Rabbit Island
The mean number of Brown Pelicans observed on Rabbit Island was 584.6
individuals (SD: ± 422, range: 0–1762), which were primarily hatch-year birds.
Survey counts were significantly different across the six weeks of observations
(χ2= 27.49, df = 5, P < 0.001; Fig. 2), with lower counts occurring in
later survey weeks relative to higher counts during earlier surveys. Throughout
the survey effort, we also positively identified 48 of the 182 individuals (26.3%
of total released; Table 2) via photograph or spotting scope from all six release
groups. Of the 48 individuals, 17 were identified on two different surveys, 7
were identified three different times, and 4 were identified on four different surveys.
Of these 48 individuals, the mean time between release and last resighting
observation was 16.3 days (SD: ± 10.40, range: 3–40 days), with the longest
time between release and last confirmed sighting being 40 days (individual Red
4Z6; 1st resight: 13 days following release, 2nd: 26 days, 3rd: 33 days, and 4th: 40
days). The longest confirmed observation of any translocated pelican was of an
2012 W. Selman, T.J. Hess, Jr., B. Salyers, and C. Salyers G7
unknown red-banded individual on 30 September (56 days post-release) at the
Cameron jetties. This individual was also the last banded bird observed during
the study (2 weeks following the end of daily counts).
Banded Brown Pelicans were observed during almost every survey (32 of 37),
with all five of the surveys that lacked banded pelicans occurring during week 6
(Fig. 2). The mean number of banded pelicans observed per survey was 6.8 (SD: ±
5.73, range: 0–20), with a maximum of 20 banded pelicans observed four days after
the first release (August 9th; 27% of banded birds available) and zero observed
on September 11, 13, 14, 16, and 17. There was a significant difference in the percent
of banded pelicans observed by week (χ2
= 20.6, df = 2, P = 0.0010; Fig. 3).
We observed a higher percentage of banded birds during week one (mean = 11.5),
Figure 2. Mean number of
pelicans observed roosting at
Rabbit Island (grey bars) and
the number of rehabilitated
pelicans released at Rabbit
Island (black line) by week.
Supplemental feeding ended
in the middle of week 5. Error
bars represent one standard
Figure 3. Percentage of translocated
Brown Pelicans observed
at Rabbit Island by
week following the initial bird
release (light grey bars) and
percentage of banded pelicans
relative to the total number of
pelicans observed (dark grey
bars). Supplemental feeding
ended on September 7, which
occurred during the middle of
week 5. Error bars represent
one standard error.
G8 Southeastern Naturalist Vol. 11, No. 1
Table 2. Resighted translocated Brown Pelicans (i.e., positively identified to individual) during
surveys of Rabbit Island (7 August to 18 September). Recovery date indicates day that pelican was
collected from the wild due to oil contamination and transferred to a rehabilitation center.
(color Recovery Release to last
leg band) date date 1st resight 2nd resight 3rd resight 4th resight sighting
A60 7/19 8/5 8/9 4
A62 7/14 8/5 8/26 21
A65 7/14 8/5 9/2 9/8 34
A75 7/15 8/6 8/26 20
A82 7/8 8/6 8/22 16
A84 7/15 8/6 9/2 27
2Z0 6/9 8/6 8/13 9/1 26
3Z1 6/6 8/6 9/2 27
3Z4 6/21 8/6 9/8 33
3Z6 6/6 8/6 8/25 8/26 8/30 9/9 34
4Z0 6/21 8/6 8/27 21
4Z2 6/6 8/6 8/25 8/29 9/1 9/8 33
4Z3 6/6 8/6 8/30 9/3 9/4 9/6 31
4Z4 6/21 8/6 8/30 24
4Z5 6/20 8/6 8/25 9/1 9/3 28
4Z6 6/18 8/6 8/19 9/1 9/8 9/15 40
4Z7 6/20 8/6 8/30 24
4Z8 6/21 8/6 9/2 27
4Z9 6/8 8/6 8/9 9/1 9/2 28
5Z0 6/20 8/6 9/2 27
6Z8 6/13 8/20 8/29 9
A87 6/4 8/20 9/1 9/2 13
A88 7/6 8/20 9/1 12
A95 6/12 8/20 8/24 9/1 12
C02 7/29 8/20 9/3 9/7 18
C04 6/24 8/20 9/2 9/3 14
C15 7/29 8/28 9/7 9/8 11
C24 8/7 8/28 9/8 11
C26 8/6 8/28 9/8 11
C28 8/4 8/28 9/4 9/9 12
C32 8/3 8/28 9/8 11
C34 8/1 8/28 9/1 3
C39 8/4 8/28 9/8 11
C45 8/8 8/28 9/8 11
C49 8/8 8/28 9/8 11
C50 8/8 8/28 9/1 9/2 4
C51 7/26 8/28 9/2 5
C52 8/1 8/28 9/3 6
C62 7/30 8/28 8/29 9/9 9/14 17
C63 8/6 9/3 9/8 5
C64 8/14 9/3 9/12 9
C73 8/7 9/3 9/6 3
C76 7/31 9/3 9/8 5
C77 8/1 9/3 9/12 9
C78 8/23 9/3 9/8 5
C81 8/10 9/10 9/15 5
C83 8/1 9/10 9/14 9/15 5
C85 8/22 9/10 9/15 5
2012 W. Selman, T.J. Hess, Jr., B. Salyers, and C. Salyers G9
and the percentage observed gradually decreased throughout the study (week six
mean = 0.89). However, the percentage of banded pelicans relative to total pelicans
observed increased significantly across weeks (χ2 = 2.66, df = 5, P = 0.041;
Fig. 3), with generally a higher percentage observed as the study progressed.
Even though Brown Pelicans were translocated to the north end of Rabbit
Island, many of these individuals integrated with the larger Brown Pelican flocks
on the southern end of the island (1.2 km SE; Fig. 4); some individuals did this
in as little as 1 day post release. In total, 264 observations of color-banded Brown
Pelicans were made at Rabbit Island, with 186 observations made on the southern
end of Rabbit Island and 78 made on the northern end. These numbers are total
banded pelicans observed and likely include recounts of individuals in subsequent
Within two weeks of initiating the supplemental feeding regimen, both translocated
and native pelicans became “habituated” to the feeding regimen and vessels.
After we ceased supplemental feeding on 7 September, we observed fewer total
pelicans at Rabbit Island (χ2 = 13.5, df = 1, P = 0.0002), as well as lower percentages
of banded pelicans (χ2 = 10.3, df = 1, P = 0.0014).
Following the initial translocation, we also observed translocated pelicans
short distances away from Rabbit Island. On August 11th (5–6 days following
Figure 4. Translocated Brown Pelican (pink C26) observed during supplemental feedings
with resident pelicans. Photograph © W. Selman (9/8/10).
G10 Southeastern Naturalist Vol. 11, No. 1
the initial release), one banded pelican was confirmed moving a short distance
away from Rabbit Island to the northern point of St. John Island (3.4 km to
ESE). On many subsequent surveys, we noted banded pelicans on a channel
marker near St. John’s Island (September; 3.7 km ESE), flying down the Calcasieu
Ship Channel (1, 2, 8, 12, 14, and 15 September; 7.8 km SE), loafing
at the Cameron Jetties Park beach (12 September; 11.0 km SSE), and perched
on the Cameron jetties (30 September; 12.0 km SSE).
It is often difficult to determine the level of mortality in animal populations
and/or during a translocation event unless tracking devices are affixed to a subsample
of individuals prior to release. Under this study’s circumstances (short
time frame, ≈5 days between notification of translocation and first bird arrival,
and request by rehabilitators), no transmitters or other tracking devices could be
affixed to determine mortality. We therefore, had to use the detection of pelican
carcasses as an indicator of mortality in this study. The ability to detect carcasses
is often quite difficult (Wobeser and Wobeser 1992), and searches are often imprecise
and/or inaccurate (Stutzenbaker 1986), primarily due to the persistence
time of carcasses on the landscape (Wobeser and Wobeser 1992). One benefit
to carcass searching for juvenile pelicans is that they are large, readily identifi-
able birds due to their large bills and white breasts. Their carcasses also seem to
persist for lengthy periods in water, since carcasses often float, or on land (W.
Selman, pers. observ.). Additionally, many pelicans from this population frequent
places that the public uses for recreational activities (i.e., Cameron Jetties Park,
Calcasieu Ship Channel, Calcasieu Lake), and dead pelicans are often reported
by the public to LDWF. During this time period, the public reported on many
dead wildlife, and we feel that it was likely that a citizen would have reported a
color-banded dead pelican.
Even though we did not observe or receive public information on translocated
pelican carcasses, we presume that there likely was some low level of
mortality due to the inability to accurately survey carcasses in all areas the
pelicans may have been. McNease et al. (1984) documented an 89.5% survival
rate of translocated Brown Pelicans two weeks after reintroduction. Along
with initial mortality rates, it is possible that translocated pelicans, particularly
juveniles, more likely succumbed to winter-associated mortality (McNease et
al. 1992). Winter mortalities are primarily driven by a lack of food supplies
and/or heavy parasite loads during sub-freezing temperatures that occurred
five months following the translocation (January and February 2011). During
the winter, we observed many native juvenile pelican carcasses, and upon
necropsy, all pelicans were found to have empty stomachs and high intestinal
parasite loads (W. Selman and J. LaCour, pers. observ.). This scenario is not
uncommon, as another study documented a large die-off of wintering Pelicanus
2012 W. Selman, T.J. Hess, Jr., B. Salyers, and C. Salyers G11
crispus Bruch (Dalmatian Pelican) in Greece, with all carcasses examined
having similar pathologies to those observed in Louisiana Brown Pelicans (Pyrovetsi
and Papazahariadou 1995).
Persistence of pelicans at Rabbit Island
We suspect that four variables worked in concert and prompted the pelican
movements observed across the latter weeks at Rabbit Island, including: 1) the
natural building of flight muscles leading to emigration from Rabbit Island,
2) unusually high tides at the end of week four that persisted into week five, 3) the
beginning of Anas discors L. (Blue-wing Teal) season and the presence of hunters
on the island during week six, and 4) the ceasing of supplemental feeding during
week five (discussed in later section).
Prior to this study, we documented Brown Pelican nesting on Rabbit Island
in early May 2010, with 5–7-week-old juveniles present on the island by
mid-June (T.J. Hess, Jr., pers. observ.). Brown Pelicans usually are capable of
flight by 11–12 weeks and can provide for themselves by 3 months (Shields
2002); almost all translocated pelicans released at Rabbit Island were capable
of flight, and therefore, both local and translocated pelicans could have started
to move away from the island at the beginning of our study (7 August). Additionally,
astronomically high tides (2.5 to 3.75 feet above mean lower low
water levels) for seven consecutive days during weeks four and five limited
the amount of dry ground available on the island, with coastal flood advisories
in effect during this period. Water completely covered the island on several
days, and the few pelicans that were observed on the island were all standing
in water. Thereafter during week six, we twice observed morning teal hunters
on the island when it was closed to waterfowl hunting. On these two days, we
observed 6 and 7 total pelicans, likely due to the disturbance of the hunters,
which has been widely documented (for review, see Madsen and Fox 1995).
However, we did not hear any shots fired by the hunters or see any pelicans
leaving the island; thus, we can only surmise that “human activity” on/near the
island altered pelican numbers those days.
One behavioral aspect of the translocated birds that deviated from local birds
was that the percentage of banded pelicans relative to the total number of pelicans
observed was significantly higher at the end of the study relative to the beginning.
This finding indicates that a larger proportion of translocated birds generally
remained at the island slightly longer than native birds. It is unknown why this
occurred, but it could be linked to the extended supplemental feedings. However,
this pattern did not continue for long, as all birds had vacated the island by the
beginning of October (following week 6 of the study).
The integration of translocated individuals into native populations is an
important factor that should be considered in any translocation study. Individuals
may readily integrate into the population or be driven away by native
G12 Southeastern Naturalist Vol. 11, No. 1
individuals (Kleiman 1989), with the worst scenario including severe harassment
and even death from local individuals (Borner 1985). During this study,
many observations were made indicating that rehabilitated Brown Pelicans
integrated successfully into local pelican populations. On several occasions,
we observed the integration of translocated pelicans with resident pelicans
(i.e., loafing, roosting, or flying with native pelicans) within one day following
their release. We did not see evidence of translocated pelicans being harassed
by resident pelicans (i.e., chased away from island) and/or social groups that
were composed of only translocated individuals. Presumably, this translocation
provided a similar scenario to the original successful translocation of Brown
Pelicans to Louisiana starting in the 1960s (Nesbitt et al. 1978). In future nesting
seasons, we will continue to monitor to determine if translocated individuals
preferentially form pair bonds with resident or translocated pelicans to further
quantify integration into the local colony.
It appears that supplemental feeding may have had an impact on the persistence
of pelicans in the vicinity of Rabbit Island until it ceased in week 5.
Cessation of feeding coincided with the other aforementioned events, but there
were significantly fewer pelicans observed at the island, as well as the percentage
of translocated pelicans observed during surveys, following the termination
of supplemental feeding. Even though these feedings provided easy forage for
rehabilitated pelicans, they were also heavily exploited by resident pelicans.
For future translocations of Brown Pelicans, we suggest that short durations of
supplemental feedings should occur, while also considering alternative feeding
strategies, including using blinds or remote feeders due to the easy habituation
of pelicans to humans.
It was difficult to determine if there were long-range movements of translocated
Brown Pelicans away from Rabbit Island. This limitation is primarily due
to the protocol of our surveys, which did not extend much outside of the Rabbit
Island colony survey area, and the inability to equip translocated/resident
hatch-year pelicans with satellite transmitters. The latter would have allowed us
to accurately document the movements of translocated individuals, as well as allow
us to quantify differences/similarities in movements of translocated pelicans
relative to local pelicans. This electronic tracking capability, however, could not
be achieved due to the immediacy of the response to the oil spill and the short
notification time (≈5 days) that we received before the first translocation event.
Some translocated pelicans may have dispersed along the coast, but we suspect
that most individuals remained in the area but just outside of our survey route;
a previous study found that most translocated Brown Pelicans in southeastern
Louisiana remained within 32 km of the release site (McNease et al. 1984). Presumably,
the low percentage of banded pelicans observed during our surveys,
2012 W. Selman, T.J. Hess, Jr., B. Salyers, and C. Salyers G13
especially toward the end of the survey period, is likely due to a combination of
these two factors. However, our observations confirm that at least some of the
182 translocated Brown Pelicans following rehabilitation remained in the vicinity
of Rabbit Island 56 days following release.
Problems with marking and resighting techniques
Throughout the study, it was difficult to readily identify translocated pelicans
using only color leg-band observations. We could not accurately identify
all banded pelicans on the island because many of the leg bands remain concealed
when pelicans were in the water, behind a group of other pelicans, far
away from the observer (especially in interior ponds at Rabbit Island), and/or
when they stood in tall grasses. Therefore, we suspect that some translocated
pelicans were uncounted in our surveys, lowering our overall percentage of
observed pelicans per survey. Further, due to the long distance of observers
from the pelicans (≈100–150 meters), the small size of the color bands, and
the inability to stabilize optics on a moving boat, positive identification of
color-banded individuals was even more difficult. However, we were able to
positively identify some birds to individual on many surveys (26% of all translocated
pelicans; Table 2, Fig. 4). Additional visual marks (i.e., paint marks,
wing streamers) could have been used to better locate translocated pelicans,
especially while flying. However, for this study, we were unable to achieve this
due to 1) the logistical difficulties between rehabilitation center and researcher
location, 2) the short time to prepare before the translocation event (≈5 days),
and 3) the decision by rehabilitators to add no additional permanent markings to
the birds in order to alleviate additional stress.
Many of our metrics to determine success/failure in this translocation were
difficult to quantify, including confirmation of marked individuals only via color
bands, mortality, and long-range movements back to oil spill areas in southeastern
Louisiana. However, in the short term, it appears that this translocation was tentatively
a success: we were able to document the persistence of some translocated
pelicans at Rabbit Island and the surrounding area, document adequate evidence
that translocated pelicans readily integrated with native pelican flocks, and that
supplemental feeding likely prolonged pelican presence at Rabbit Island. Along
with short-term monitoring, we will continue to conduct long-term monitoring
of the Rabbit Island pelican colony, including: 1) documenting the number of
translocated pelicans that return to nest at the island and 2) determining if translocated
pelicans preferentially pair with native or other translocated pelicans.
Both of these aspects are critical to further understanding the long-term success
or failure of this translocation. For future pelican translocations, we recommend
that a subset of individuals be equipped with radio/satellite transmitters to better
document movements and mortality, as well as that additional auxiliary markers
G14 Southeastern Naturalist Vol. 11, No. 1
be used to better identify translocated individuals through resighting. Coordinated
monitoring on a larger scale would also improve the ability of researchers
to determine mortality, persistence, and movements. Supplemental feedings
should use strategies that will alleviate human/boat habituation such as blinds
and remote-controlled feeders. It would also be beneficial to secure Rabbit Island
as a bird sanctuary for the Brown Pelican nesting colony and other colonial nesting
wading birds. This protection would prevent excessive human disturbance to
nesting birds from hunters, recreational fishermen, and commercial crabbers that
access interior portions of the island via tidal channels.
We would like to thank Scott Quinn (British Petroleum [BP]) and Matt Bell (Global
Pollution Services [GPS]) for their support in coordinating and compiling the resources
necessary to complete the translocation and follow-up monitoring. During the translocation,
monitoring, and supplemental feeding, we are grateful for the assistance of LDWF
Rockefeller staff Brett Baccigalopi, Chance Baccigalopi, Kim Bourriaque, and Ron Hebert
and GPS boat captains Sterling Constance, Travis Constance, and Jeremy Robbins.
We would also like to thank the veterinary staff and assistants that provided their time
and service during the rehabilitation and translocations, including but not limited to:
Jim LaCour (LDWF), Rhonda Murgatroyd (Wildlife Response Services), Louise Clemency
(USFWS), Luis Padilla (Smithsonian Institute), and Kevin Castle (National Park
Service). All banding was performed under the USGS Bird Banding Laboratory Permit
#22884. Scott Walter, Susan DeVries, and two anonymous reviewers provided helpful
comments that improved the paper. This paper is dedicated to the LDWF employees and
all others who spent endless hours in southeastern Louisiana to battle the oil spill and the
ill effects it had on Louisiana’s wildlife.
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