Predator Exclusion for Piping Plover
1 NOTES from Dr. D:
2 -----The running head should be italicized, which it is not in this paper.
3 -----Your final paper will NOT have double-spacing, nor numbered lines – that was ONLY for
4 the rough draft.
5 -----NOTICE how, in the Methods section, Krista clumped the different papers that she read
6 into the types of exclosures used in each paper. She did an excellent job on this section.
7 -----The Results section might be a bit short, although she then summarizes the results from
8 ALL the papers in Table 1 – an EXCELLENT thing to do!!!
9 -----In the Discussion section she groups the papers into those that used method “A” and
10 those that used method “B” and… so on, and then discusses the effectiveness of each
11 method. This is exactly what we are looking for – your ability to categorize, summarize, and
12 synthesize information into a new, coherent whole. At the end she emphasizes some of the
13 issues involved in the studies (predators, time, distance, etc.
14 -----She has done the Table exactly right: the list of Tables and Figures on one page, then the
15 actual Table, or Figure, on a separate page
16
17 -----The paper is not completely perfect, but it is a good example of where you should be.
18 Thank you, Krista, for sharing it with the class.
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Predator Exclusion for Piping Plover
19 EFFECTS OF PREDATOR EXCLUSION ON THE REPRODUCTIVE SUCCESS OF THE
20 PIPING PLOVER (CHARADRIUS MELODUS).
21 Krista K. Schmidt, Wildlife Conservation and Management student, School of Natural
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Resources, 325 Biological Sciences East, The University of Arizona, Tucson, AZ 85721,
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1 kristaks@email.arizoan.edu
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41 Abstract
42
The main threat to piping plover (Charadrius melodus) survival and reproductive
43 success is nest depredation. Different methods exist to try to reduce piping plover nest
44 predation including the use of predator exclusion techniques such as using predator
45 exclosures, electric fences and chick shelters. A literature search analysis of 11 different
46 predator exclusion studies revealed that using both electric fencing and predator exclosures
47 at the same time is the most effective method for increasing mean piping plover fledge rate
48 above 1.5 chicks/breeding pair, the minimum reproductive rate described to be necessary for
49 a successful breeding season as outlined in different piping plover recovery plans. I
50 recommend the continued practice of using both exclsoures and electric fences to protect
51 piping plover nests as well as trying to develop new techniques to improve piping plover
52 reproductive success.
53 Key Words Charadrius melodus, electric fence, predator exclosure, predator management,
54 piping plover
55 —―—―—―—―—
56
The piping plover (Charadrius melodus) is a small, compact sandy-colored shorebird
57 with thin, orange legs, a black chest band that can be complete or broken, and a black beak
58 with an orange base (Kaufman 2000). In the summer it nests on beaches along the Atlantic
59 coast and on salt flats and other open areas near lakes and rivers in the northern Great
60 Plains. In the winter the piping plover migrates to the beaches and mudflats on the southeast
61 coast (Haig et al. 2005). Piping plovers typically tend to nest closer to vegetation and dunes,
62 farther away from water, closer to tern nests and farther from other piping plover nests
63 (Burger 1987). After incubating for about 25 days, the baby piping plovers hatch with a downy
64 coat, ready to run and feed themselves. The parents lead their young down to the water's
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65 edge to feed on small invertebrates in the sand (Atlantic Coast Piping Plover Recovery Team
66 1996).
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Since the start of the 20th century, uncontrolled hunting and egg collecting had lowered
68 the piping plover population drastically. Some populations on the Atlantic Coast were almost
69 extirpated due to these uncontrolled practices. With the passage of the Migratory Bird Treaty
70 Act in 1918 and a decline in the popularity of feathers in the fashion industry, the plover
71 numbers was able to recover somewhat (Haig and Oring 1985). During the late 1940s to early
72 1950s the piping plover numbers began to decline again due to various natural and
73 anthropogenic causes (Atlantic Coast Piping Plover Recovery Team 1996). In 1985 the piping
74 plover was listed as an endangered species under the Endangered Species Act of 1973 (U.S.
75 Fish and Wildlife Service). Since then critical habitat has been set aside for the piping plover
76 and recovery plans and conservation programs in many of the states that make up the
77 plover's summer and winter ranges have been put into action (Atlantic Coast Piping Plover
78 Recovery Team 1996, U.S. Fish & Wildlife Service).
79
Current threats to the continued survival of the piping plover include: loss and
80 degradation of breeding and wintering habitat, a shrinking gene pool, disturbance by human
81 visitors and their pets, motorized vehicles, human introduced predators such as cats, dogs,
82 rats, beach cleaners, oil spills and other types of contaminants, and predation (Atlantic Coast
83 Piping Plover Recovery Team 1996). Out of all of those, predation, especially of the plover's
84 nests and young, is considered to be the biggest threat next to loss and degradation of
85 breeding and wintering habitat (Lauro and Tanacredi 2002, Patterson et al. 1991, U. S. Fish
86 and Wildlife 2003).
87
Predator control methods have been used in piping plover recovery and conservation
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88 plans since the 1980s in an effort to slow the decline of their numbers and to promote their
89 recovery (Atlantic Coast Piping Plover Recovery Team 1996, U.S. Fish & Wildlife Service
90 2003) . Types of predator control in general include predator barriers, deterrents, removal and
91 recruitment reduction. Of these categories, predator barriers, particularly predator exclosures
92 and electric fences, are the most commonly used types of predator control for protecting
93 piping plover nests and young (Mabee and Estelle 2000, Mayer and Ryan 1991).
94
Given the use of predator exclusion devices to protect piping plover nests, the obvious
95 question arises: what sort of effect do predator exclusion techniques have on the reproductive
96 success of the piping plover? I answered this question by conducting a literature search
97 looking for studies that researched the effects of the use of different predator exclusion
98 techniques on piping plover nesting success, fledge rate and daily survival rates. With nest
99 depredation being the biggest threat to piping plover nests it should be that using predator
100 exclusion techniques around piping plover nests will impart greater reproductive success than
101 leaving nests unprotected and vulnerable to predators.
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Methods
Types of predator exclusion devices.— Predator exclosures consist of a circle, square
104 or triangle shaped cage of galvanized wire mesh fencing, usually with some sort of netting on
105 top to reduce avian predation, that is placed around the nest to keep medium to large
106 predators away from the nest. The size of exclosures vary from small to large. Long stakes
107 are usually attached to the mesh fence cage and are placed in holes dug by a post hole
108 digger and then filled in to keep the predator exclosure from falling or blowing over. Other
109 methods of securing the exclosure are also used. The holes in the mesh fencing have to be
110 big enough for the plovers to be able to enter the exclosure with easy but small enough to
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111 keep out predators larger than the parents (Deblinger et al. 1992, Melvin et al. 1992, Murphy
112 et al. 2003A). See Fig. 1.
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Electric fencing usually consists of a some sort of galvanized metal wire and an electric
114 current generator that runs low voltage electricity through the wire itself, giving a mild shock to
115 anything that touches the fence. Electric fencing can be something as simple as wire elevated
116 off the ground using stakes or rods or can be woven into mesh fencing or chicken wire, again
117 held up by stakes or rods. The wire is attached at both ends to the electric current generator
118 to create a complete electrical circuit. Like predator exclosures, any electric fencing used
119 needs to be high enough for the adult plovers to pass underneath, but high enough so that
120 predators taller than the adult plovers cannot cross under it. Electric fencing can be used to
121 block off an entire section of beach or be used as a second barrier around a single piping
122 plover nest in addition to using a predator exclosure (Mayer and Ryan 1991, Murphy et al.
123 2003A, Maxon et al. 1996). See Fig. 1.
124
Another, less commonly used type of predator exclusion device are chick shelters.
125 Chick shelters are simple structures created by nailing two pieces of rectangular plywood
126 together to form an “open-ended tent” which the chicks can hide from avian predators
127 underneath. They are simple to make, set up and take down, making them a cost-effective
128 type of predator exclusion device (Burness and Morris 1992, Kruz et al. 2002). See Fig 2.
129
Methods for my literature search analysis— I separated the different types of predator
130 exclusion techniques into four categories: no protection, use of predator exclosures only, use
131 of electric fences only and use of both predator exclosures and electric fences. The variables
132 that I examined were mean nesting success (%), mean fledge rate (chicks/breeding pair), and
133 mean daily survival rate (%). I chose a minimum fledge rate of 1.5 chicks per breeding pair for
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134 the basis of determining if using a particular predator exclusion method was successful or not.
135 My reasoning behind choosing the 1.5 chicks/pair came from the mean recovery rate
136 objectives of three different piping plover recovery plans. The Atlantic Coast Population
137 Revised Recovery Plan for the piping plover calls for a mean productivity rate of 1.5 fledged
138 chicks per breeding pair for the recovery plan to be successful (Atlantic Coast Piping Plover
139 Recovery Team 1996). Likewise the recovery plan for the Great Lakes piping plover calls for
140 1.5-2.0 fledglings per pair (U. S. Fish and Wildlife Service 2003) and the recovery strategy of
141 the piping plover in Canada calls for at least 1.25 fledges per pair (Environment Canada
142 2006).
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144
Results
Eleven studies were analyzed for the effects that different predator exclusion decisions
145 had on piping plover (Charadrius melodius) nesting success, fledge rate and daily survival
146 rate (see Table 1). Out of the 11 studies, 9 reported mean nesting success percentages, 8
147 reported mean fledge rates and 6 reported mean daily survival rates. Out of the three
148 variables taken from the 11 studies analyzed, there were 20 different mean nest success
149 reported, 22 different fledge rates reported and 9 different daily survival rates reported. By
150 using a productivity objective of 1.5 fledges per mating pair as a requirement for declaring
151 success or failure of predator exclusion techniques, 6 studies reported failure when using no
152 protection, 3 studies reported success and 4 studies reported failure when using only predator
153 exclosures, 3 studies reported failure when only using electric fencing, and 6 studies reported
154 success when using both predator exclosures and electric fences (see Table 1).
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Discussion
When it came to improving mean nesting success and mean fledge rate, using both
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157 predator exclosures and electric fences has more success than using either electric fences or
158 predator exclosures alone. This fact has important implications for the continued conservation
159 of piping plovers (Charadrius melodus) during their nesting season. There are both pros and
160 cons to using this method of predator exclusion for piping plover nests. For one, it can be both
161 costly and labor intensive to construct, set up and take down and maintain electric fences and
162 exclosures, moreso for exclosures than for electric fences (Johnson and Oring 2002, Larson
163 et al. 2003, Melvin et al. 1992, Schmelzeisen et al. 2004). Also equipment malfunctions that
164 are not quickly discovered can easily lead to nest failure because of depredation (Mayer and
165 Ryan 1991, Melvin et al. 1992, Murphy et al. 2003B).
166
The third, less commonly used predator exclusion technique is the application of chick
167 shelters near the nests of shorebirds. Having been used successfully at least tern (Sternula
168 antillarum) colonies (Mueller 1981), the idea of using chick shelters near piping plover nests
169 has merit. Other studies have suggested that chick shelters be used for piping plover chicks
170 (Alberta Piping Plover Recovery Team 1996, Schmelzeisen et al. 2004). Kruse et al. (2001)
171 reported that chick shelters had no effect on piping plover chick survival. More information on
172 the effectiveness of using chick shelters as a predator exclusion method for nesting piping
173 plovers is needed before chick shelters should be used in piping plover conservation
174 decisions.
175
Predator exclusion methods can even have negative effects for piping plovers.
176 Sometimes exclosures actually increase predation of adult piping plovers at the exclosures ,
177 (Murphy et al. 2003B). The use of exclosures and electric fences can have varying effects
178 (Ivan and Murphy 2005, Larson et al. 2002, Maxon and Haws 2000, Mayer and Ryan 1991
179 and Murphy et al. 2003A). But while nesting success may increase, exclosures do not always
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180 increase fledging success or daily survival rate (Mabee and Estelle 2000, Maxon and Haws
181 2000, see Table 1).
182
One very important thing to consider when making a decision about using predator
183 exclusion for piping plover nests is the predator community of the surrounding area. Knowing
184 what types of predators inhabit the region that the piping plover nesting area is located in is
185 key to developing a successful predator exclusion management plan (Ivan and Murphy 2005,
186 Johnson and Oring 2002, Mabee and Estelle 2000). Electric fences are useful for deterring
187 mammalian predators (Ivan and Murphy 2005). Predator exclosures while having some effect
188 of keeping out mammalian predators are also useful at keeping out avian predators (Mayer
189 and Murphy 1991, Schmelzeisen et al. 2004). When both electric fences and predator
190 exclosures are used, piping plover nesting success and fledge rate is higher than either
191 unprotected nests or nests protected by just predator exclosures or electric fencing alone
192 (Ivan and Murphy 2005, Larson et al. 2002, Larson et al. 2003, Murphy et al. 2003 A, see
193 Table 1). One downside to electric fences and predator exclosures is that they do not prevent
194 nest depredation by small predators like weasels, snakes or small birds (Johnson and Oring
195 2002).
196
There are some cautions associated with predator exclusion techniques that should be
197 considered when deciding whether to use such management decisions. Time spent setting up
198 predator exclusion devices should be kept brief so the adult plovers can return to their nests
199 as soon as possible and to reduce the chance of nests being abandoned (Atlantic Coast
200 Piping Plover Recovery Team 1996). Disturbance of the nests when setting up predator
201 exclusion devices should be kept to a minimum and and further monitoring of the nests
202 should take place at a far distance from any nests to reduce nest abandonment by the
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203 parents and to prevent attracting the attention of predators to the nests (MaCiver et al. 1990,
204 Melvin et al. 1992, Strang 1980). Equipment should be checked regularly for breeches or
205 malfunctions and be kept in good shape if it is to be able to do a proper job of keeping
206 predators away from piping plover nests (Mayer and Ryan 1991, Schmelzeisen et al. 2004).
207
Johnson and Oring (2002) cautions that using electric fencing and predator exclosures
208 is only a temporary measure and that other large-scale and long-term management options
209 need to be developed while Larson et al. (2002) optimistically states that if increases in
210 conservation efforts are made, that it is possible that the Great Plains piping plover population
211 can actually reverse the downward trend that it is currently experiencing. Either way, this
212 study provides evidence that using both electric fences and predator exclosures is a
213 successful method of reducing piping plover nest predation and increasing nesting success
214 and fledge rate. I would recommend the continued use of both in tandem with further research
215 on different alternate predator management options.
216
Literature Cited
217 Atlantic Coast Piping Plover Recovery Team. 1996. Piping plover Atlantic coast population
218
revised recovery plan. population status and distribution. U. S. Fish and Wildlife
219
Service, Hadley, Massachusetts.
220 Burger, J. 1987. Physical and social determinants of nest-site selection in piping plover in
221
New Jersey. Condor 89:811—818.
222 Burness, G. P., and R. D. Morris. 1992. Shelters decrease gull predation on chicks at a
223
common tern colony. Journal of field Ornithology 63:186—189.
224 Deblinger, R. D., J. J. Vaske, and D. W. Rimmer. 1992. An evaluation of different predator
225
exclosures used to protect Atlantic coast piping plover nests. Wildlife Society Bulletin
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226
20:274—279.
227 Engley, L., and D. Prescott. 2005. Use of predator exclosures to protect piping plover nests in
228
Alberta, 1998-2001. Technical report, T-2005-002, produced by Alberta Conservation
229
Association, Edmonton, Alberta, Canada. 18 pp.
230 Environment Canada. 2006. Recovery Strategy for the Piping Plover (Charadrius melodus
231
circumcinctus) in Canada. Species at Risk Act Recovery Strategy Series. Environment
232
Canada, Ottawa, Canada. 30 pp.
233 Haig, S. M., C. L. Ferland, F. J. Cuthbert, J. Dingledine, J. P. Goossen, A. Hecth and N.
234
McPhillips. 2005. A complete species census and evidence for regional
235
declines in piping plovers. Journal of Wildlife Management 69:160–173.
236 Haig, S.M. and L.W. Oring. 1985. The distribution and status of the piping plover throughout
237
the annual cycle. Journal of Field Ornithology 56: 266-273.
238 Ivan, J. S. and R. K. Murphy. 2005. What preys on piping plover eggs and chicks? Wildlife
239
Society Bulletin 33:113—119.
240 Johnson, M. and L. W. Oring. 2002. Are nest exclosures an effective tool in plover
241
conservation? Waterbirds 25:184—190.
242 Kaufman, K. 2000. Kaufman field guide to birds of North America. Houghton Miffilin Company,
243
New York, USA.
244 Kruse, C. D., K. F. Higgins and B. A. Vander Lee. 2002. Influence of predation on piping
245
plover, Charadrius melodus, and least tern, Sterna antillarum, productivity along the
246
Missouri River in South Dakota. Canadian-Field Naturalist 115:480-486.
247 Larson, M. A., M. R. Ryan and R. K. Murphy. 2002. Population viability of piping plovers:
248
effects of predator exclusion. Journal of Wildlife Management 66:361—371.
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249 Larson, M. A., M. R. Ryan and R. K. Murphy. 2003. Assessing recovery feasibility for piping
250
plovers using optimization and simulation. Wildlife Society Bulletin 31:1105—1116.
251 Lauro, B. and J. Tanacredi. 2002. An examination of predatory pressures on piping plovers
252
nesting at Breezy Point, New York. Waterbirds 25:401—409.
253 Mabee, T. J. and V. B. Estelle. 2000. Assessing the effectiveness of predator exclosures for
254
plovers. The Wilson Bulletin 112:14—20.
255 MaCivor, L. H., S. M. Melvin, and C. R. Griffin. 1990. Effects of research activity on piping
256
plover nests. Journal of Wildlife Management 54:443—447.
257 Marxson, S. J. and K. V. Haws. 2000. Population studies of piping plovers at Lake of the
258
Woods, Minnesota: 19 year history of a declining population. Waterbirds 23:475—481.
259 Maxon, S. J., S. A. Mortensen, D. J. Goodermote and C. S. Lapp. 1996. Success and failure
260
of ring-billed gull deterrents at common tern and piping plover colonies in Minnesota.
261
Colonial Waterbirds19:242—247.
262 Mayer, P. M. and M. R. Ryan. 1991. Electric fences reduce mammalian predation on Piping
263
Plover nests and chicks. Wildlife Society Bulletin 19:59—63.
264 Melvin, S. M., L. H. MacIvor and C. R. Griffin. 1992. Predator exclosures: a technique to
265
reduce predation at piping plover nests. Wildlife Society Bulletin 20:143—148.
266 AMueller, N. S. 1981. Chick shelters decrease avian predation in least tern colonies on
267
Nantucket Island, Massachusetts. Journal of field Ornithology 53:58—60.
268 BMurphy, R. K., R. J. Greenwood, J. S. Ivan and K. A. Smith. 2003. Predator exclusion
269
methods for managing endangered shorebirds: are two barriers better than one?
270
Waterbirds 26:156—159.
271 Murphy, R. K., I. M. Michaud, D. R. Prescott, J. S. Ivan, B. J. Anderson and M. L. FrenchSchmidt
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272
Pombier. 2003. Predation on adult piping plovers at predator exclosure cages.
273
Waterbirds 26:150—155.
274 Patterson, M. E., J. D. Fraser, and J. W. Roggenbuck. 1991. Factors affecting piping plover
275
productivity on Assateague Island. Journal of Wildlife Management 55:525—531.
276 Rimmer, D. W. and R. D. Deblinger. 1990. Use of predator exclosures to protect piping plover
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nests. Journal of Field Ornithology 61:217—233.
278 Schmelzeisen, R., D. R. C. Prescott, and L. Engley. 2004. Methods for controlling depredation
279
on piping plovers in Alberta: a literature review and synthesis. Alberta Species at Risk
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Report No. 84. Edmonton, Alberta, Canada. 29 pp.
281 Strang, C. A. 1980. Incidence of avian predators near people searching for waterfowl nests.
282
The Journal of Wildlife Management 44:220—222.
283 U.S. Fish & Wildlife Service [FWS]. Species Profile: Piping Plover (Charadrius melodus).
284
<http://ecos.fws.gov/speciesProfile/SpeciesReport.do?spcode=B079>. Accessed 20
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Feb 2008.
286 U.S. Fish & Wildlife Service. 2003. Recovery plan for the Great Lakes piping plover
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(Charadrius melodus). U.S. Fish & Wildlife Service, Fort Snelling, Minnesota.
288
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289
Tables and Figures
290 Table 1. Summary of effects of different predator exclusion techniques on nesting success,
291 fledge rate and daily survival rate of piping plovers (Charadrius melodus) complied from
292 different predator exclusion studies.
293
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294 Table 1
Study
Kruse et al. 2001
Predator
exclusion
technique
Mean Daily
Mean Nest Mean Fledge Rate Survival Rate
Success (%)
(chicks/pair)
(%)
no protection
61.6%
exclosure
34.1%
chick shelter
Murphy et al. 2003
Larson et al. 2003
Ivan and Murphy 2005
Larson et al. 2002
Maybee and Estelle 2000
Predator Exclusion
Technique Successful
(Fledge Rate >1.5)?
no effect
no protection
45.0%
0.72
no
exclosure
exclosure and
electric fence
84.0%
1.73
yes
98.0%
2.06
yes
no protection
0.89
no
exclosure
1.28
no
s
exclosure and
permanent
electric fence
permanent
electric fence
1.78
yes
2.25
yes
1.15
no
no protection
32.0%
exclosure
exclosure and
electric fence
66.0%
1.35
no
73.0%
1.56
yes
1.28
no
1.78
yes
1.15
no
2.25
yes
exclosure
exclosure and
temporary
electric fence
permanent
electric fence
exclosure and
permanent
electric fence
no protection
75.0%
exclosure
60.0%
no protection
44.0%
1.2
exclosure
74.8%
1.0
Melvin et al. 1992
no protection
17.0%
0.12
93.0%
no
exclosure
90.0%
1.96
94.40%
yes
Engley and Prescott 2001
no protection
24.5%
exclosure
34.4%
Mayer and Ryan 1991
no protection
35.0%
Maxon and Haw s 2000
97.6%
98.8%
no
no
96.06%
97.00%
0.65
33.00%
no
295
296
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297 Figure 1. Circular predator exclosure with mesh top surrounded by an electrified wire fence
298 (http://www.state.nj.us/dep/fgw/ensp/images/som/plovelecfnc.jpg).
299 Figure 2. A chick shelter near a common tern (Sterna hirundo) nest (Burness and Morris
300 1992).
301
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302 Figure 1.
303
304
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305 Figure 2.
306
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