Notes from Dr. D

-----The running head should be italicized, which it is not in this paper.

-----Your final paper will NOT have double-spacing, nor numbered lines – that was ONLY for the rough draft.

-----NOTICE how, in the Methods section, Krista clumped the different papers that she read into the types of exclosures used in each paper. She did an excellent job on this section.

-----The Results section might be a bit short, although she then summarizes the results from ALL the papers in Table 1 – an EXCELLENT thing to do!!!

-----In the Discussion section she groups the papers into those that used method “A” and those that used method “B” and… so on, and then discusses the effectiveness of each method. This is exactly what we are looking for – your ability to categorize, summarize, and synthesize information into a new, coherent whole. At the end she emphasizes some of the issues involved in the studies (predators, time, distance, etc.

-----She has done the Table exactly right: the list of Tables and Figures on one page, then the actual Table, or Figure, on a separate page
-----The paper is not completely perfect, but it is a good example of where you should be. Thank you, Krista, for sharing it with the class.

EFFECTS OF PREDATOR EXCLUSION ON THE REPRODUCTIVE SUCCESS OF THE PIPING PLOVER (CHARADRIUS MELODUS).

Krista K. Schmidt, Wildlife Conservation and Management student, School of Natural

Resources, 325 Biological Sciences East, The University of Arizona, Tucson, AZ 85721,

USA¹

The main threat to piping plover (Charadrius melodus) survival and reproductive success is nest depredation. Different methods exist to try to reduce piping plover nest predation including the use of predator exclusion techniques such as using predator exclosures, electric fences and chick shelters. A literature search analysis of 11 different predator exclusion studies revealed that using both electric fencing and predator exclosures at the same time is the most effective method for increasing mean piping plover fledge rate above 1.5 chicks/breeding pair, the minimum reproductive rate described to be necessary for a successful breeding season as outlined in different piping plover recovery plans. I recommend the continued practice of using both exclsoures and electric fences to protect piping plover nests as well as trying to develop new techniques to improve piping plover reproductive success.

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The piping plover (Charadrius melodus) is a small, compact sandy-colored shorebird with thin, orange legs, a black chest band that can be complete or broken, and a black beak with an orange base (Kaufman 2000). In the summer it nests on beaches along the Atlantic coast and on salt flats and other open areas near lakes and rivers in the northern Great Plains. In the winter the piping plover migrates to the beaches and mudflats on the southeast coast (Haig et al. 2005). Piping plovers typically tend to nest closer to vegetation and dunes, farther away from water, closer to tern nests and farther from other piping plover nests (Burger 1987). After incubating for about 25 days, the baby piping plovers hatch with a downy coat, ready to run and feed themselves. The parents lead their young down to the water's edge to feed on small invertebrates in the sand (Atlantic Coast Piping Plover Recovery Team 1996).

Since the start of the 20^th century, uncontrolled hunting and egg collecting had lowered the piping plover population drastically. Some populations on the Atlantic Coast were almost extirpated due to these uncontrolled practices. With the passage of the Migratory Bird Treaty Act in 1918 and a decline in the popularity of feathers in the fashion industry, the plover numbers was able to recover somewhat (Haig and Oring 1985). During the late 1940s to early 1950s the piping plover numbers began to decline again due to various natural and anthropogenic causes (Atlantic Coast Piping Plover Recovery Team 1996). In 1985 the piping plover was listed as an endangered species under the Endangered Species Act of 1973 (U.S. Fish and Wildlife Service). Since then critical habitat has been set aside for the piping plover and recovery plans and conservation programs in many of the states that make up the plover's summer and winter ranges have been put into action (Atlantic Coast Piping Plover Recovery Team 1996, U.S. Fish & Wildlife Service).

Current threats to the continued survival of the piping plover include: loss and degradation of breeding and wintering habitat, a shrinking gene pool, disturbance by human visitors and their pets, motorized vehicles, human introduced predators such as cats, dogs, rats, beach cleaners, oil spills and other types of contaminants, and predation (Atlantic Coast Piping Plover Recovery Team 1996). Out of all of those, predation, especially of the plover's nests and young, is considered to be the biggest threat next to loss and degradation of breeding and wintering habitat (Lauro and Tanacredi 2002, Patterson et al. 1991, U. S. Fish and Wildlife 2003).

Predator control methods have been used in piping plover recovery and conservation plans since the 1980s in an effort to slow the decline of their numbers and to promote their recovery (Atlantic Coast Piping Plover Recovery Team 1996, U.S. Fish & Wildlife Service 2003) . Types of predator control in general include predator barriers, deterrents, removal and recruitment reduction. Of these categories, predator barriers, particularly predator exclosures and electric fences, are the most commonly used types of predator control for protecting piping plover nests and young (Mabee and Estelle 2000, Mayer and Ryan 1991).

Given the use of predator exclusion devices to protect piping plover nests, the obvious question arises: what sort of effect do predator exclusion techniques have on the reproductive success of the piping plover? I answered this question by conducting a literature search looking for studies that researched the effects of the use of different predator exclusion techniques on piping plover nesting success, fledge rate and daily survival rates. With nest depredation being the biggest threat to piping plover nests it should be that using predator exclusion techniques around piping plover nests will impart greater reproductive success than leaving nests unprotected and vulnerable to predators.

Methods

Types of predator exclusion devices.— Predator exclosures consist of a circle, square or triangle shaped cage of galvanized wire mesh fencing, usually with some sort of netting on top to reduce avian predation, that is placed around the nest to keep medium to large predators away from the nest. The size of exclosures vary from small to large. Long stakes are usually attached to the mesh fence cage and are placed in holes dug by a post hole digger and then filled in to keep the predator exclosure from falling or blowing over. Other methods of securing the exclosure are also used. The holes in the mesh fencing have to be big enough for the plovers to be able to enter the exclosure with easy but small enough to keep out predators larger than the parents (Deblinger et al. 1992, Melvin et al. 1992, Murphy et al. 2003^A). See Fig. 1.

Electric fencing usually consists of a some sort of galvanized metal wire and an electric current generator that runs low voltage electricity through the wire itself, giving a mild shock to anything that touches the fence. Electric fencing can be something as simple as wire elevated off the ground using stakes or rods or can be woven into mesh fencing or chicken wire, again held up by stakes or rods. The wire is attached at both ends to the electric current generator to create a complete electrical circuit. Like predator exclosures, any electric fencing used needs to be high enough for the adult plovers to pass underneath, but high enough so that predators taller than the adult plovers cannot cross under it. Electric fencing can be used to block off an entire section of beach or be used as a second barrier around a single piping plover nest in addition to using a predator exclosure (Mayer and Ryan 1991, Murphy et al. 2003^A, Maxon et al. 1996). See Fig. 1.

Another, less commonly used type of predator exclusion device are chick shelters. Chick shelters are simple structures created by nailing two pieces of rectangular plywood together to form an “open-ended tent” which the chicks can hide from avian predators underneath. They are simple to make, set up and take down, making them a cost-effective type of predator exclusion device (Burness and Morris 1992, Kruz et al. 2002). See Fig 2.

Methods for my literature search analysis— I separated the different types of predator exclusion techniques into four categories: no protection, use of predator exclosures only, use of electric fences only and use of both predator exclosures and electric fences. The variables that I examined were mean nesting success (%), mean fledge rate (chicks/breeding pair), and mean daily survival rate (%). I chose a minimum fledge rate of 1.5 chicks per breeding pair for the basis of determining if using a particular predator exclusion method was successful or not. My reasoning behind choosing the 1.5 chicks/pair came from the mean recovery rate objectives of three different piping plover recovery plans. The Atlantic Coast Population Revised Recovery Plan for the piping plover calls for a mean productivity rate of 1.5 fledged chicks per breeding pair for the recovery plan to be successful (Atlantic Coast Piping Plover Recovery Team 1996). Likewise the recovery plan for the Great Lakes piping plover calls for 1.5-2.0 fledglings per pair (U. S. Fish and Wildlife Service 2003) and the recovery strategy of the piping plover in Canada calls for at least 1.25 fledges per pair (Environment Canada 2006).

Results

Eleven studies were analyzed for the effects that different predator exclusion decisions had on piping plover (Charadrius melodius) nesting success, fledge rate and daily survival rate (see Table 1). Out of the 11 studies, 9 reported mean nesting success percentages, 8 reported mean fledge rates and 6 reported mean daily survival rates. Out of the three variables taken from the 11 studies analyzed, there were 20 different mean nest success reported, 22 different fledge rates reported and 9 different daily survival rates reported. By using a productivity objective of 1.5 fledges per mating pair as a requirement for declaring success or failure of predator exclusion techniques, 6 studies reported failure when using no protection, 3 studies reported success and 4 studies reported failure when using only predator exclosures, 3 studies reported failure when only using electric fencing, and 6 studies reported success when using both predator exclosures and electric fences (see Table 1).

When it came to improving mean nesting success and mean fledge rate, using both predator exclosures and electric fences has more success than using either electric fences or predator exclosures alone. This fact has important implications for the continued conservation of piping plovers (Charadrius melodus) during their nesting season. There are both pros and cons to using this method of predator exclusion for piping plover nests. For one, it can be both costly and labor intensive to construct, set up and take down and maintain electric fences and exclosures, moreso for exclosures than for electric fences (Johnson and Oring 2002, Larson et al. 2003, Melvin et al. 1992, Schmelzeisen et al. 2004). Also equipment malfunctions that are not quickly discovered can easily lead to nest failure because of depredation (Mayer and Ryan 1991, Melvin et al. 1992, Murphy et al. 2003^B).

The third, less commonly used predator exclusion technique is the application of chick shelters near the nests of shorebirds. Having been used successfully at least tern (Sternula antillarum) colonies (Mueller 1981), the idea of using chick shelters near piping plover nests has merit. Other studies have suggested that chick shelters be used for piping plover chicks (Alberta Piping Plover Recovery Team 1996, Schmelzeisen et al. 2004). Kruse et al. (2001) reported that chick shelters had no effect on piping plover chick survival. More information on the effectiveness of using chick shelters as a predator exclusion method for nesting piping plovers is needed before chick shelters should be used in piping plover conservation decisions.

Predator exclusion methods can even have negative effects for piping plovers. Sometimes exclosures actually increase predation of adult piping plovers at the exclosures , (Murphy et al. 2003^B). The use of exclosures and electric fences can have varying effects (Ivan and Murphy 2005, Larson et al. 2002, Maxon and Haws 2000, Mayer and Ryan 1991 and Murphy et al. 2003^A). But while nesting success may increase, exclosures do not always increase fledging success or daily survival rate (Mabee and Estelle 2000, Maxon and Haws 2000, see Table 1).

One very important thing to consider when making a decision about using predator exclusion for piping plover nests is the predator community of the surrounding area. Knowing what types of predators inhabit the region that the piping plover nesting area is located in is key to developing a successful predator exclusion management plan (Ivan and Murphy 2005, Johnson and Oring 2002, Mabee and Estelle 2000). Electric fences are useful for deterring mammalian predators (Ivan and Murphy 2005). Predator exclosures while having some effect of keeping out mammalian predators are also useful at keeping out avian predators (Mayer and Murphy 1991, Schmelzeisen et al. 2004). When both electric fences and predator exclosures are used, piping plover nesting success and fledge rate is higher than either unprotected nests or nests protected by just predator exclosures or electric fencing alone (Ivan and Murphy 2005, Larson et al. 2002, Larson et al. 2003, Murphy et al. 2003^A, see Table 1). One downside to electric fences and predator exclosures is that they do not prevent nest depredation by small predators like weasels, snakes or small birds (Johnson and Oring 2002).

There are some cautions associated with predator exclusion techniques that should be considered when deciding whether to use such management decisions. Time spent setting up predator exclusion devices should be kept brief so the adult plovers can return to their nests as soon as possible and to reduce the chance of nests being abandoned (Atlantic Coast Piping Plover Recovery Team 1996). Disturbance of the nests when setting up predator exclusion devices should be kept to a minimum and and further monitoring of the nests should take place at a far distance from any nests to reduce nest abandonment by the parents and to prevent attracting the attention of predators to the nests (MaCiver et al. 1990, Melvin et al. 1992, Strang 1980). Equipment should be checked regularly for breeches or malfunctions and be kept in good shape if it is to be able to do a proper job of keeping predators away from piping plover nests (Mayer and Ryan 1991, Schmelzeisen et al. 2004).

Johnson and Oring (2002) cautions that using electric fencing and predator exclosures is only a temporary measure and that other large-scale and long-term management options need to be developed while Larson et al. (2002) optimistically states that if increases in conservation efforts are made, that it is possible that the Great Plains piping plover population can actually reverse the downward trend that it is currently experiencing. Either way, this study provides evidence that using both electric fences and predator exclosures is a successful method of reducing piping plover nest predation and increasing nesting success and fledge rate. I would recommend the continued use of both in tandem with further research on different alternate predator management options.

Literature Cited

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Burger, J. 1987. Physical and social determinants of nest-site selection in piping plover in New Jersey. Condor 89:811—818.

Burness, G. P., and R. D. Morris. 1992. Shelters decrease gull predation on chicks at a common tern colony. Journal of field Ornithology 63:186—189.

Deblinger, R. D., J. J. Vaske, and D. W. Rimmer. 1992. An evaluation of different predator exclosures used to protect Atlantic coast piping plover nests. Wildlife Society Bulletin 20:274—279.

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Alberta, 1998-2001. Technical report, T-2005-002, produced by Alberta Conservation

Association, Edmonton, Alberta, Canada. 18 pp.

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Kruse, C. D., K. F. Higgins and B. A. Vander Lee. 2002. Influence of predation on piping plover, Charadrius melodus, and least tern, Sterna antillarum, productivity along the Missouri River in South Dakota. Canadian-Field Naturalist 115:480-486.

Larson, M. A., M. R. Ryan and R. K. Murphy. 2002. Population viability of piping plovers: effects of predator exclusion. Journal of Wildlife Management 66:361—371.

Larson, M. A., M. R. Ryan and R. K. Murphy. 2003. Assessing recovery feasibility for piping plovers using optimization and simulation. Wildlife Society Bulletin 31:1105—1116.

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^AMueller, N. S. 1981. Chick shelters decrease avian predation in least tern colonies on Nantucket Island, Massachusetts. Journal of field Ornithology 53:58—60.

^BMurphy, R. K., R. J. Greenwood, J. S. Ivan and K. A. Smith. 2003. Predator exclusion methods for managing endangered shorebirds: are two barriers better than one? Waterbirds 26:156—159.

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Schmelzeisen, R., D. R. C. Prescott, and L. Engley. 2004. Methods for controlling depredation on piping plovers in Alberta: a literature review and synthesis. Alberta Species at Risk Report No. 84. Edmonton, Alberta, Canada. 29 pp.

Strang, C. A. 1980. Incidence of avian predators near people searching for waterfowl nests. The Journal of Wildlife Management 44:220—222.

U.S. Fish & Wildlife Service [FWS]. Species Profile: Piping Plover (Charadrius melodus). . Accessed 20 Feb 2008.

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Table 1. Summary of effects of different predator exclusion techniques on nesting success, fledge rate and daily survival rate of piping plovers (Charadrius melodus) complied from different predator exclusion studies.

Figure 1. Circular predator exclosure with mesh top surrounded by an electrified wire fence (http://www.state.nj.us/dep/fgw/ensp/images/som/plovelecfnc.jpg).

Figure 2. A chick shelter near a common tern (Sterna hirundo) nest (Burness and Morris 1992).

Figure 1.