A Review of Thirty-five Years of Osprey (Pandion haliaetus) Nesting ...

A Review of Thirty-five Years of Osprey (Pandion haliaetus)
Nesting Data in Rhode Island
By
Eric S. Walsh
Photo by David Windsor
A MAJOR PAPER SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIRMENTS
FOR THE DEGREE OF MASTER OF ENVIRONMENTAL SCIENCE AND MANAGEMENT
UNIVERSITY OF RHODE ISLAND
JULY 30, 2013
MAJOR PAPER ADVISOR: Dr. Peter Paton
MESM TRACK: Conservation Biology

Introduction
The osprey (Pandion haliaetus) is one of North America’s most magnificent,
recognizable, and unique birds of prey. They are a pandemic species, found on every continent
except Antarctica and inhabit both inland and coastal regions in the breeding and non-breeding
season. In North America, most ospreys are migratory breeding from Florida north through
Newfoundland and west through Canada and southern Alaska and then south through the west
coast and sections of Montana, Idaho, Wyoming, Colorado, Arizona, and Utah (Henny et al.
2010). In New England, they breed along the south coast of Connecticut east to Massachusetts
and north along the coast. They are also found along inland lakes and streams in Maine, New
Hampshire, and Vermont. RI’s breeding population are present between April and August and
are located predominantly along the south coast and throughout Narragansett Bay.
They are taxonomically unique being in a monotypic genus Pandion and family
Pandionidae. Their closest relatives are from the class Accipitiforms, which includes eagles and
kites. They are piscivores foraging almost exclusively on a diet of fish (Poole 1989) in shallow
tidal zones along the coast (Prevost 1979) and clear shallow freshwater bodies (Vana-Miller
1987). They do not generally discriminate among fish species when foraging (Hughes 1983)
except probably being more successful targeting slower benthic species (Flemming and Smith
1990) than picsivorous species that are more weary (Vana-Miller 1987).
Prior to the use of DDT ospreys were common up and down the eastern seaboard. In the
1950’s-60’s, the osprey’s population began to decline because of the use of organochlorine
pesticides (Ames 1966). DDT accumulates up the food chain, eventually reaching birds of prey
causing thin eggshells resulting in breakage during incubation and ultimately nesting failure
1

(Wiemeyer et al. 1975). In the 1940’s, breeding surveys estimated ~1000 nests between New
York and Boston. By the end of the 60’s, nest sites declined by 98.5% to 150 active nests
(Spitzer & Poole 1980). In 1972, the Federal Government banned DDT, and then in 1976, the
osprey was listed as an Endangered Species by the U.S. Fish and Wildlife Service. Since then,
the osprey began to recover and was up-graded to “Threatened” in 1982 and “Special Concern”
in 1999. Today, the IUCN list the osprey as Least Concern. In the United States, ospreys have
recovered to 16,000-19,000 breeding pairs in 2001, and they have been proposed as a sentinel
species for contaminate investigations because they fit the criteria well (Henny et al. 2010).
Many conservation recovery programs and citizen monitoring programs focus their
attention on monitoring and managing osprey populations because of their previous sharp
decline. In 1977, the Rhode Island Department of Environmental Management (RIDEM) began
monitoring the state’s osprey population as it recovered from the effects of DDT. Staff biologists
and volunteers observed all known nests in Rhode Island and recorded how many chicks fledged
each year. In 2010, with cooperation from RIDEM, the Audubon Society of Rhode Island
(ASRI) assumed management of this successful program. In 1977, there were 12 Active nest
sites and 7 successful nests compared to 2012 with 126 Active nests, and 96 successful nests
(unpublished ASRI data).
Osprey population recovery has been associated with nest structure type and availability
(Reese 1977, Henny and Kaiser 1996), habitat suitability (Toschik et al. 2006), contaminate
concentrations (Henny et al. 1977, Toschik et al. 2006), food resource availability (Poole 1982,
Eriksson 1986), proximity to conspecific nesters (Toschik et al. 2006), and human activity
(Levenson and Koplin 1984). North Atlantic coastal populations have recovered at variable rates
2

(Henny et al. 1977, Spitzer and Poole 1977) exhibiting variable reproductive rates over time and
space (Henny et al. 2010).
Historically, they nest on coniferous and deciduous tall dead trees (Berger & Mueller,
1969) or live trees (MacCarter 1972), utility poles (Prevost 1977), cellular towers, and artificial
nesting platforms (Newton 1980). Within heterogeneous landscapes, nest site locations have
been found to change over time (Bai et al. 2009) and the effects of landscape context on nest
success is varied (Swenson 1981, Lohmus 2001). They typically choose sites with an
unobstructed view of the surrounding landscape (Van Daele & Van Daele 1982). Coastal
populations usually nest close to foraging resources along shallow tidal wetlands. Inland
populations will typically nest and subsequently travel 3-5 km (Vana-Miller 1987, Poole 1989)
to forage at shallow water bodies and as much as 14 km if necessary (Hagan and Walters 1990).
Artificial nesting structures often provide access to nesting habitat that would otherwise not be
suitable for nesting (Newton 1980). These structures are usually placed in open saltwater
marshes allowing for close proximity to forgaing ground with an open unobstructed view.
The RI osprey breeding data has not been fully analyzed. In the past, only nest status
metrics and reproductive rates have been reported. Little was known about the location of nest
sites within the Rhode Island landscape and their change over time. Until recently, the structure
types were unknown for Rhode Island’s breeding population. Subsequently the relationship
between structure type and breeding success in Rhode Island had not been explored.
The objective of this paper was to review the Rhode Island osprey nesting data between
1977 and 2012 and describe the observed trends. The second objective was to identify areas of
3

esearch opportunity or additional analyses that will provide insight into the dynamics of a
population that repopulated a landscape after a population bottleneck.
Methods
Database and Monitoring
All analyses were conducted on a data set collected in the State of Rhode Island from
1977 to 2012. Each year volunteers would monitor each known osprey nest site between April
and July, documenting the status of the nest sites each month and the number of young observed.
The Rhode Island Department of Environmental Management (DEM) originally implemented
the nest-monitoring program until 2008. In 2009, the program was transferred to the Audubon
Society of Rhode Island (ASRI), which implemented data collection in 2010. Subsequently,
there are no data for nesting season 2009.
The data for each year consisted of the status of each nest and the number of fledglings
produced for each successful nest. Each year every nest was categorized as one of the following:
Inactive, Subadult/Housekeeping (starting in 2010 nest sites that showed signs of osprey activity
but not nesting behavior such as incubation posture, were labeled as Housekeeping instead of
Subadult to align with the prevailing evidence that not all nest sites with non-incubating pairs are
necessarily Subadults), Active, and Successful. Active sites were nests that showed signs of
nesting or young rearing, but failed to produce fledglings. Nest sites were identified based on
passive discovery of active sites. Potential nest sites were monitored after a report was made of
the possibility of an active nesting pair. There was no active effort to identify nest sites around
the state.
4

The original data I used were in three forms. The first was a spreadsheet with nest names
and nesting history for nest sites between 1977 and 2008. The second was a summary of each
year’s nest status between 1977-2012, which included the number of Inactive, Subadult, Active,
Successful nest sites, and Fledglings with calculations for the number of fledglings per Active
and Successful nest site. The third form was a GIS database that contained the spatial location of
most nest sites and the status of each site for each monitored year. The nesting history data in the
GIS originated from the spreadsheet data. However, the first database did not correspond
perfectly to the GIS records because not every nest site was in the GIS. The reason was
unknown; therefore, the analyses were conducted on the GIS data and the results do not perfectly
correspond to the original summary data published by the DEM and ASRI.
Data QA
In an effort to improve the spatial information of each monitored nest site, the Audubon
Society of Rhode Island hired three interns for the 2012 nesting season to record the spatial
location and structure type of every monitored site in 2012 (N=200). All nest sites being
monitored in 2012 were visited, as a result, there were nests (N=64) used in these analyses,
which spatial and platform type were not explicitly confirmed.
To improve the accuracy of the data, I investigated the discrepancies for each year where
the GIS summary did not align with the summary data. For several of the monitored years, there
were DEM published osprey newsletters that contained individual nest data. When possible, I
cross-referenced the published and spreadsheet data with the GIS data. However, it was not
possible to assess every nest because in several instances, nest names were not consistent
5

through the years, and there was no available information to trace nest name changes. I used the
newsletters first and then the spreadsheet when correcting the GIS data.
Data Analysis
I summarized the data to provide insight into nesting trends between 1977 and 2012. I
analyzed the average distance between nest sites using a Hawth’s Tools Euclidean distance
calculation in ArcGis 9.3. I analyzed the difference between structure type and fledgling
production using an ANOVA with significance of α

monitored years (1977-2012) into four cohorts and associated each cohort to an imagery year
(Table 1). I used ArcGIS 9.3 to process the imagery and produce the buffer zone rasters.
The buffer zone and entire state LULC imagery were analyzed using Fragstats 4.1
(McGarigal 2012). I analyzed the entire state’s land cover to compare the distribution of cover
types within the buffer zone to cover types over the entire state. I report percent land cover of the
selected cover types.
Results
The Osprey population has increased 10.27 fold from 11 Active nest sites in 1977 to 124
Active sites in 2012, of the 124 Active sites in 2012, 94 were successful (Figure 1). The number
of fledglings produced each year has increased from 10 in 1977 to 164 in 2012 (Figure 2). The
success rate or average number of fledglings per successful nest has ranged from 2.7-1.5 with an
average of 1.9(SD=+/- 0.2) fledglings per year (Figure 3). There was no detectable change in the
overall percent change in the number of fledglings produced from year to year (average=11.6%
SD=+/-28.4%). The reproductive rate has ranged from 0.9 to 1.8 and has averaged 1.4 (+/-0.3)
(Figure 4). The reproductive rate is based on the number of fledglings per active nest; it is lower
than the success rate and is a measure of the health of a population.
The ospreys have built their nests on a variety of structures. There are eight primary
structure types; these include platform, telephone, cell, tree, other, channel. A platform is any
manmade structure specifically erected with the intent to support an osprey nesting pair. Usually,
these platforms are approximately 10’-14’ tall (this category also includes telephone poles that
are intentionally erected as osprey nest platforms) and located in marsh habitat or in close
7

proximity to foraging habitat. The telephone category represents manmade structures that are not
intentionally erected for osprey breeding, but are subsequently used as a nest site. This category
includes high-tension electric poles and telephone poles. Nest sites built on light poles are in the
structure category Light. The light category is for any structure that has a light or set of lights at
the top, such as athletic field lights. The cell category is for nests built on cell phone towers and
the channel category is for the few nest sites built on channel markers. The tree sites are in the
tree category, and finally the other category is for all sites that do not fit into any of the other
categories. For example, a nest built on a water tower would be classified as other.
Between 1977 and 2012 of the known structure types, 37% of the nest sites were built on
platforms, 20% on telephone poles, 11% on light poles, 8% on cell phone towers, and 6% on
trees. Between 1977 and 1989, the predominate structure type was telephone poles, but after
1987, platform structures increased in use from 7 - 54 structures, an 87% increase (Figure 5).
Cell towers were the second greatest used structure in 2012 with 24, which was the last known
year of a steady increase in Cell tower use that began 2008 with 10 towers.
Platforms produced an average of 1.43 fledglings while cell towers produced 1.64 per
year, the greatest average number of fledglings. Telephone poles produced an average of 1.35
fledglings per year and trees 1.53 (Figure 6). There was a significant difference between yearly
fledgling production F(34,1308), p=

significant difference between structure success rates F(6,194)=3.76, p=0.001. A Post Hoc
Tukey test showed that the differences were between platforms and cell towers (p adj =0.02), and
unknown and cell towers (p adj

increased from 10% to 29% in 1977 to 2012 respectively. During this same period, overall urban
land cover increased from 13% to 22%. Another land cover shift is open water. Open water
comprised 5.9% of the total area within 3 km of the nest sites, while 4.3% of the total landscape.
The amount of open water within the buffer zones decreased to 4.3% in 2012 and the total
landscape had 4.2% open water. There was an overall decrease in the percent cover of deciduous
wetlands, mixed forest, herbaceous wetlands, and open water and overall increase in urban land
cover that exceeded expected changes given the proportion of each in the entire landscape (Table
2). Overall nest sites were located within landscapes with more deciduous wetlands, herbaceous
wetlands, and urban land cover and less coniferous forest, mixed forest, and deciduous forest
then would be expected given the overall landscape distribution (Table 3).
Discussion
The Rhode Island osprey population is recovering from the observed decline in the
1950’s and 60’s caused by organochlorine pesticides. The recovery has shown yearly
fluctuations in Active and Successful nests with the two being closely synchronous within most
years. The exception was between 1988 and 1994 when the number of Active nests increased
from 23 to 43, a 47% increase but Successful nests increased from 19 to 26 a 27% increase. The
influx of breeding ospreys grew faster than the production of young. In addition, between 1988
and 1994, the average number of fledglings produced per successful nest decreased from 2.2 in
1988 to 1.7 in 1994. Interestingly, 2.2 was the highest the fledgling/successful nest rate has been
to date. If fledglings per successful nest rate did not decrease over the same period, then the
cause of a pair not producing at least one fledgling would be independent of the entire
10

population’s ability to produce young. Since the evidence shows the entire population declined in
fledgling production, it leads to the possibility that there were environmental or density
dependent deterministic events driving the decline. A possible reason for this pattern was the
inability of the fish stock to support the foraging needs of the breeding population (Van Daele &
Van Daele 1982). At this time, I did not have fish stock data to test this theory. Another
possibility is the increase or influx of young naïve nesting pairs with little experience.
The pattern of slow successful nest growth in comparison to active nest growth would
eventually produce a depression or decline in active nest sites when the young nesting cohorts
from the depressed successful years reached breeding age. Ospreys reach sexual maturity at age
three to four (Poole 1989), so the 1988 cohort of young would have been at breeding age in
1991. The Active nest numbers did not decline in 1991, to the contrary they continued to
increase for three more years. This is a possible indication that the Active nest numbers were
increasing do to an influx of naïve nesters from outside of the Rhode Island breeding population.
Further supporting the naïve nester theory was the fledgling per successful nest rate. New nesting
pairs are not as successful as mature nesting pairs (Poole 1989). Since the 1988 to 1994 rate
decreased from 2.2 to 1.7 (Figure 3), then the slow growth in Successful nests may have been a
function of a young population and not a depressed fish stock.
The synchronous pattern between Active and Successful nests should be looked at with
caution though. Active sites are a measure of previous years’ success rate as an Active nest is an
indication of the start of nesting. Success is a representation of within year factors affecting
nesting. A depressed success rate is an indication of environmental factors affecting within year
fledgling production leading to an effect on active nest rates in the future. Between 2000 and
2002, the number of active nests increased from 56 to 87. In 1997, the number of successful
11

nests was 37 and in 1999, the number of successful nests increased to 54. The young from 1997
would correspond to the breeding cohort of 2000 and 1999 would correspond to 2002. Hence, an
increase in successful nests produces an increase in breeding adults three years later (Figure 1).
The reproductive rate or average fledgling per Active nest site fluctuated over 35 years
between the highest at 1.8 in 1983, 1988, and 2000 to its lowest point in 1977 and 1981 at 0.9.
The rate was always above the critical replacement rate of 0.8 (Spitzer and Poole 1980) and in
comparison to populations in the Chesapeake Bay area and west in Idaho, Rhode Island’s was
more robust (Van Daele & Van Daele 1982, Watts and Paxton 2007). However, populations in
Europe have shown reproductive rates as high as 2.04 (Saurola 2005). There appears to be no
pattern in relation to the successful nest rate. The reproductive rate is an indication of the
population’s ability to produce young within an area. This number is affected by environmental
stochastity, deterministic events, and breeder’s maturity. The breeding population on average has
not increased its fledgling production from year to year; the percent change in fledgling
production has varied above and below zero (Figure 14). The increase in fledglings observed in
Figure 2 is a function of the increase in population size and not the environments ability to
support an increase in the production of young.
Structure
Ospreys in Rhode Island preferred to nest on platforms almost twice as often as any other
structure (Figure 15). Platforms also supported the greatest number of successful nest sites
(Figure 16). Platforms historically are located in and along coastal wetlands (Figure 17). In
Rhode Island, this would be the prime habitat for nesting, providing the ospreys with access to
extensive areas of shallow water. Among all structure types, platform use showed the greatest
12

increase and at the greatest rate (Figure 5). Between 2002 and 2012, platform use increased at a
rate of 2.3 per year, the next closest was cell towers and telephone poles at 0.6 per year. There
was a statistically significant difference between the average number of successful platform and
cell tower nest sites. On average, cell towers produced more successful nests than platforms, but
this may be shifting. The percentage of successful nests on cell structures appears to be
decreasing while the percentage of successful platform and telephone nests are increasing
(Figure 7, 8, 9). However, the observed cell tower pattern may be a function of small sample
size, between 1984 and 1997only one tower was active and successful. Compared to 2012, 23
cell towers were active. Across all structures, there was no difference in fledgling production.
This is different from other osprey populations that produced more offspring on artificial
structures (Van Daele & Van Daele 1982). The lack of difference is an indication that the
structure and any correlations with structure types, i.e. location (since each structure type would
be within a specific landscape type) has no significant affect on reproductive rates. Open coastal
waters accounted for 22% of the area within 3 km of nest sites and this value was relatively
consistent through the years (Figure 18). One theory is the close proximity to and vast expanse of
available foraging habitat negates any difference in fledgling production that might occur
because of differences in structure type. These analyses did not quantify the average land cover
type surrounding a structure type, but anecdotally, platforms are typically erected in open salt
marshes, telephone poles are typically in utility right-of-ways, cell towers and light poles are
usually in urban landscapes. Structures are therefore in a diversity of landscapes and still equally
successful at producing young.
13

Landscape Context
Nest sites were located in landscapes dominated by Urban, Deciduous and Herbaceous
Wetlands, and Coastal Waters. The landscape context of nesting sites changed over time. As the
population increased, more nest sites were located in urban landscapes in greater proportion than
the entire landscape (Table 3). The RI osprey population appears to not only do well in human
dominated landscapes, but also seek nest locations within urban landscapes. Other studies have
found that ospreys are not as successful within human influenced landscapes (Swenson 1979,
Van Daele & Van Daele 1982). Bai et al. (2009) found that an osprey population in Germany
shifted their use of land cover from forested areas to agricultural. The RI population did shift
away from forested landscapes but to urban landscapes (Table 2). The RI population probably
did not make the shift to agriculture, because agriculture comprises a small percentage of the
total landscape (5.3%). However, Bai et al. suggested that the shift they observed was due to the
eutrophication of water bodies surrounding agriculture landscapes, which increase water body
productivity. Urban landscapes can have a similar effect through nutrient runoff, a possible
explanation of ospreys nesting in the RI urban landscape. Another explanation is the pattern of
human development intersects osprey site selection patterns. Ospreys in Rhode Island nest along
coastal areas, and humans tend to settle intensely along coastal regions. The observed pattern
could be a byproduct of human development trends.
The distance between nest sites also changed over time. There was a decrease in the
average distance between active nest sites. The decrease was not linear though. Overall, there
was an approximate decline of 5000 meters between nest sites. The decline occurred gradually in
some years and then sharply in others. There were three sharp declines, the first was between
1977 and 1981, then again between 1989 and 1992, and the last appears recently between 2007
14

and 2012. The sharp declines appear to correspond with an increase in active nest sites. It
appears that as the population increases, ospreys are nesting near conspecifics when possible and
then expanding their range into new territory. Hence, the increases in nesting distance after the
sharp declines in distance. Ospreys gain protection from predators by nesting in colonies (Hagan
and Walters 1990) but there may be other benefits and costs of colonial nesting. Bretagnolle et
al. (2008) found a similar pattern in nest distance among colonizing ospreys in a western
Mediterranean population. They found periods of decline, followed by periods of stability where
provisioning rate and prey size increased as the density of ospreys increased, however
productivity decreased. The RI population exhibited the same pattern of decline in reproductive
success while the distance between nest sites decreased. The reproductive rate declined from 1.8
to 1.0 between 1988 and 1993, encompassing the same period when nesting distance declined
sharply, e.g. increase in nest density (Figure 4). One area of future research is analyzing clusters
of nest sites and how they change over time and how reproductive metrics are influenced.
Conclusion
The RI osprey population is increasing and there is no indication at this time that the
population is stabilizing. The growth is occurring with the support of artificial platforms. Based
on the pattern of colonization and reproductive rate, platform location should be within 2 km of
other nest sites, but an effort to locate platforms in areas without existing nest structures should
be made. This would ease the density dependent effects observed in osprey populations. In
addition, based on observed patterns, nest sites should be located in areas with deciduous and
15

herbaceous wetlands within 3 km, and urban landscapes do not appear to negatively affect
ospreys, so selecting locations within an urban landscape may benefit ospreys in RI.
Future research should focus on understanding the dynamics between fish stocks and
yearly production. In addition, contaminant exposure can affect population growth, so an
assessment of potential contaminates that are affecting the RI population is recommended.
Because the Rhode Island population bottlenecked and is repopulating near urban land cover, an
in-depth review of the effects of landscape on site selection, population distribution, nesting
behavior, and success should be a focus of future research.
16

Literature Cited
Ames, P. (1966). DDT Residues in the Eggs of the Osprey in the North-Eastern United States
and Their Relation to Nesting Success. Journal of Applied Ecology , 3, 87-97.
Bai, M.L., D. Schmidt, E. Gottschalk, and M. Muhlengerg. (2009) Distribution pattern of an
expanding Osprey (Pandion haliatus) population in a changing environment. Journal of
Ornithology, 150: 255-263
Berger, D. and A. H. Mueller. (1969) Ospreys in Northern Wisconsin. in J.J. Hickey, ed.
Peregrine falcon populations: their biology and decline. , 340-341.
Bretanolla, V., F. Mougeot, and J.-C. Thibault. (2008) Density dependence in a recovering
osprey population: demographic and behavioural processes. Journal of Animal Ecology.
77: 998-1007
Eriksson, M. O. G. (1986) Fish delivery, production of young, and nest density of Osprey
(Pandion haliaetus) in southwest Sweden. Canadian Journal of Zoology. 64: 1961-19
Flemming, S.P. & Smith, P.C.C. (1990). Environmental influences on Osprey foraging in
Northeastern Nova Scotia. Journal of Raptor Research. 24 (3): 64–67.
Hagan, J.M. III and J.R. Walters. (1990) Foraging behavior, reproductive success, and colonial
nesting in ospreys. Auk, 107: 506-521
Henny, C. J. and J. L. Kaiser. (1996) Osprey Population Increase Along the Willamette River,
Oregon, and the Role of Utility Structures, 1976–1993’, in D. M. Bird, D. E. Varland and
J. J. Negro(eds), Raptors in Human Landscapes, Academic Press, Ltd., London, pp. 97–
108
17

Henny, C.J., M.A. Byrd, J.A. Jacobs, P.D. Mclain, M.R. Todd, and B.F. Halla. (1977) Mid-
Atlantic coast Osprey populations: present numbers, productivity, pollutant
contamination, and status. Journal of Wildlife Management. 41: 254-265
Henny, C.J., R.A. Grove, J. L. Kaiser, and B.L. Johnson. (2010) North American Osprey
Populations and Contaminants: Historic and Contemporary Perspectives. Journal of
Toxicology and Environmental Health, Part B. 13: 579-603
Hughes, J. (1983) On Osprey habitat and productivity: a tale of two habitats. In Bird, D.M., ed.
Biology and Management of Bald Eagles and Ospreys. Harpell Press, Ste. Anne De
Bellevue, Quebec. pp 269-273
Levenson, H. and A. J. Koplin. (1984) Effects of human sctivity on productivity of nesting
ospreys. The Journal of Wildlife Management 48 (4), 1374-1377.
Lohmus, A. (2001) Habitat selection in a recovering Osprey Pandion haliaetus population. Ibis
143: 652-657
MacCarter, D. (1972). Reproductive performance and population trends of osprey at Flathead
Lake, Montana. M.S. Thesis , 80.
McGarigal, K., SA Cushman, and E Ene. (2012). FRAGSTATS v4: Spatial Pattern Analysis
Program for Categorical and Continuous Maps. Computer software program produced by
the authors at the University of Massachusetts, Amherst. Available at the following web
site: http://www.umass.edu/landeco/research/fragstats/fragstats.html
Newton, I. (1980). The role of food in limiting bird numbers. Ardea 68 (1), 11-30.
18

Poole, A.F. (1982) Brood reduction in temperate and sub-tropical Ospreys. Oecologia 53: 111-
119
Poole, A.F. (1989) A Natural and unnatural history. Cambridge University Press, NY.
Prevost, Y. (1977) Feeding ecology of osprey in Antigonish County, Nova Scotia. M.S. Thesis ,
111.
Reese, J. G. (1969) A Maryland Osprey population 75 years ago and today. Maryland Birdlife
25:116-119
Saurola, P. (2005) Monitoring and conservation of Finnish ospreys Pandion haliaetus in 1971-
2005. Status of Raptor Populations in Eastern Fennoscandia. Proceedings of the
workshop, Kostomuksha, Karelia, Russia, November 8-10, 2005.
Spitzer, P. and A.F. Poole. (1980) Coastal Ospreys between New York City and Boston.
American Birds , 34 (3), 234-241.
Swenson, J. E. (1979) Factors affecting status and reproduction of ospreys in Yellowstone
National Park. Journal of Wildlife Management. 43:595-601.
Swenson, J. E. (1981) Osprey nest site characteristics in Yellowstone National Park. Journal of
Field Ornithology, 52(1): 67–69.
Toschik, P. C., M. C. Christman, B. A. Rattner, and M. A. Ottinger. (2006) Evaluation of
Osprey Habitat Suitability and Interaction with Contaminant Exposure. Journal of
Wildlife Management. 70 (4): 977-988
19

Van Daele, L., & Daele, a. H. (1982) Factos affecting the productivity of ospreys nesting in
west-central Idaho. Condor. 84 (1): 292-299.
Vana-Miller, S. (1987) Habitat Suitability Index Models. Biological Reports 82 (10.154): 46.
Watts, B.D. and B.J. Paxton. (2007) Ospreys of the Chesapeake Bay: population recovery,
ecological requirements, and current threats. Waterbirds. 30: 39-49
Wiemeyer, S. N., Spitzer, P. R., Krantz, W. C., & Cromartie, T. G. (1975). Effects of
Environmental Pollutants on Connecticut and Maryland Ospreys. The Journal of Wildlife
Management , 39 (1), 124-139.
20

Appendix A
140
Total Number of Active and Sucessful Nest
Sites
# of Nests
120
100
80
60
40
20
0
Active
Successful
Figure 1. The total recorded number of Active and Successful osprey nest sites in Rhode Island between 1977 and 2012.
Number of Fledglings
Total Number of Osprey Fledglings
200
180
160
140
120
100
80
60
40
20
0
1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 2010 2012
Figure 2. The total number of observed osprey fledglings in Rhode Island between 1977 and 2012.
21

3.0
Average Number of Fledglings per Successful
Nest Site
Number of Fledglings
2.5
2.0
1.5
1.0
0.5
0.0
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2010
2011
2012
Figure 3. The average number of osprey fledglings per successful nest in Rhode Island between 1977 and 2012.
2.0
Average Number of Fledgelings per Active
Nest
Number of Fledglings
1.5
1.0
0.5
0.0
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2010
2011
2012
Figure 4. The average number of osprey fledglings per Active nest, also known as the reproductive rate with the
replacement rate of 0.08 (Blue Line).
22

60
Number of Active Nests per Year
50
Number of Ative Nests
40
30
20
10
cell
light
platform
telephone
tree
0
Figure 5. The number of Active osprey nests in Rhode Island per year per structure type between 1977 and 2012.
2.50
Average Number of Fledglings per Structure
Type
2.00
Number of Fledglings
1.50
1.00
0.50
0.00
cell channel light other platform telephone tree unknown
Figure 6. The average number of osprey fledglings per structure type in Rhode Island between 1977 and 2012.
23

1.4
Average Percent Successful Nests per Structure
Type
1.2
1
Percent
0.8
0.6
0.4
0.2
0
cell light other platform telephone tree unknown
Figure 7. The average percent Successful osprey nest site per structure type in Rhode Island between 1977 and 2012.
1.2
Percent Successful Cell Tower Nest Sites of the
Active Sites
1
0.8
0.6
0.4
0.2
0
Figure 8. The percent Successful osprey nest sites of the Active Cell tower structured nest sites in Rhode Island between
1977 and 2012.
24

1.2
Percent Successful Platform Nest Sites of the
Active Sites
Percent
1
0.8
0.6
0.4
0.2
0
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2010
2011
2012
Figure 9. The percent Successful osprey nest sites of the Active Platform structured nest sites in Rhode Island between
1977 and 2012.
1.2
Percent Successful Telephone Nest Sites of the
Active Sites
Percent
1
0.8
0.6
0.4
0.2
0
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2010
2011
2012
Figure 10. The percent Successful osprey nest sites of the Active Telephone structured nest sites in Rhode Island between
1977 and 2012.
25

8000
Average Distance Between Nest Sites
7000
6000
Distance (m)
5000
4000
3000
2000
1000
0
Figure 11. The average distance between osprey nest sites in Rhode Island between 1977 and 2012.
60.0%
50.0%
40.0%
30.0%
20.0%
10.0%
0.0%
Distribution of Land Cover within Rhode
Island
1972
1985
1999
2010
Figure 12. The overall distribution of land cover types in Rhode Island in 1972, 1985, 1999, and 2010.
26

50.0%
45.0%
40.0%
35.0%
30.0%
25.0%
20.0%
15.0%
10.0%
5.0%
0.0%
Distribution of Land Cover within 3 km of
Osprey Nest Sites
1972
1985
1999
2010
Figure 13. The distribution of land cover types within 3km of osprey nest sites in Rhode Island in 1972, 1985, 1999, and
2010.
140.0
120.0
100.0
80.0
60.0
40.0
20.0
0.0
-20.0
-40.0
Percent Change of Fledglings from Previous
Year
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2010
2011
2012
Figure 14. The percent change of osprey fledglings in Rhode Island from the previous year's total production between
1977 and 2012.
27

700
Total Number of Active Nest Sites per
Structure Type
664
Number of Active Nest Sites
600
500
400
300
200
100
0
360
308
206
103
141
2 11
channel other tree cell light unknown telephone platform
Figure 15. The total number of Active osprey nest sites in Rhode Island per structure type between 1977 and 2012.
Number of Successful Nest Sites
600
500
400
300
200
100
0
Total Number of Successful Nest Sites per
Structure Type
0 9
78
116
channel other tree cell light unknown telephone platform
170
218
279
520
Figure 16. The total number of Successful osprey nest sites in Rhode Island per structure type between 1977 and 2012.
28

Figure 17. The distribution of all nest sites in Rhode Island as of 2012.
29

Percent Area
35.0
30.0
25.0
20.0
15.0
10.0
5.0
0.0
Percent Area of Land Cover within 3km of
Nest Sites Fixed for Open Coastal Water
1972
1985
1999
2010
Figure 18. The percent of land cover within 3 km of osprey nest sites in RI adjusted for the amount of coastal water.
Imagery/Model Year Cohort of Years Number of Years Number of Nests
1972 1977-1981 4 19
1985 1982-1992 11 56
1999 1993-2003 11 119
2010 2004-2010 6 205
Table 1. The imagery years used in the land cover analyses and the associated nesting years.
30

RI Land Cover
Change
Buffer Land
Cover Change Difference
Agriculture 5.2% 5.9% 0.8%
Coniferous Forest 2.8% 3.1% 0.2%
Coniferous Wetland -0.3% -0.7% -0.5%
Deciduous Forest -27.6% -27.6% 0.0%
Deciduous Wetland 1.0% -4.8% -5.8%
Herbaceous
Wetland -1.3% -2.6% -1.3%
Mixed Forest 9.9% 6.5% -3.4%
Urban 8.5% 18.7% 10.2%
Open Water 0.0% -1.5% -1.5%
Table 2. The percent change of each of the 12 categories of land cover for the entire state of Rhode Island and the 3
km buffer zones surrounding each nest site between 2010 and 1972. The far right column indicates the difference
between the overall change within the buffers and the total landscape. For example, there was an increase in
Agriculture between 1972 and 2010 by 5.2% and within the buffer zone by 5.9%. Therefore, Agriculture increased
within the buffer zone over the entire landscape by 0.8%. The areas highlighted in yellow are considered significant
increases or decreases in land cover use compared to the entire landscape.
1972 1985 1999 2010
Average
Difference
over Time
Agriculture 0.0% 1.3% 0.8% 0.7% 0.7%
Coniferous Forest ‐1.2% ‐2.3% ‐0.9% ‐1.0% ‐1.3%
Coniferous
Wetland 0.4% 0.2% 0.0% ‐0.1% 0.1%
Deciduous Forest ‐5.7% ‐6.1% ‐8.4% ‐5.7% ‐6.5%
Deciduous Wetland 6.1% 4.0% 1.0% 0.2% 2.8%
Herbaceous
Wetland 2.3% 1.6% 1.1% 0.9% 1.5%
Mixed Forest ‐0.3% ‐2.4% ‐1.5% ‐3.7% ‐2.0%
Urban ‐3.4% 2.4% 6.7% 6.8% 3.1%
Open Water 1.5% 0.9% 0.5% 0.1% 0.8%
Table 3. The percent difference between the 3 km osprey nest buffer zone and the entire Rhode Island
landscape for of each of the 12 categories of land cover for each year. The far right column indicates the
average difference between the overall change within the buffers and the total landscape. For example, on
average the landscape within 3 km of an osprey nest site had 6.5% less Deciduous Forest than would be
expected given the total coverage of Deciduous Forest for the state. The highlighted values are considered
significant because they are greater than 1%.
31