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Raptor Research and Management Techniques - Chapter: 10 Page: 171 - ACCESSING NESTS

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171

I

Accessing Nests

Equipment

JOEL E. PAGEL

RUSSELL K. THORSTROM

Santa Cruz Predatory Bird Research Group,
100 Shaffer Road, Santa Cruz, CA 95060 U.S.A.

The Peregrine Fund,

5668 West Flying Hawk Lane, Boise, ID 83709 U.S.A.

CLIFF- AND TREE-ENTRY TECHNIQUES

Raptors nesting on trees, cliffs or cliff-like structures (bridges, buildings, towers, etc.) create unique circumstances for safe access to nests, eggs, and young. Entries should be limited to biologists who are (I) comfortable with heights, (2) have direct knowledge and handling experience with the species in question, and (3) are thoroughly familiar with safe climbing and rappelling techniques.

Entry to nests, as well as to hunting perches for diet studies, should be undertaken only with sufficient knowledge of the nest or ledge location and the current state of the nesting chronology (see Chapter 19). Searches for nests during climbs or rappels are potentially dangerous, both to the birds and the climber. Noting the exact location of the nest with a photograph taken at an appropriate scale, and recording the azimuth from the observation point to the nest, or having a ground spotter will help the climber locate the best route to the nest.

Ropes. Static, semi-static, and dynamic ropes each have their place for tree and cliff research. Static lines have limited stretch, are extremely durable, and are suitable for very long rappels (70 m or more) and tree work, but may be less convenient on smaller cliffs. Static lines are bulky and inflexible, making them more difficult to use on short-distance nest entries. They should never be used for lead climbing where short or long falls are possible.

Dynamic ropes are used for standard rappels, and climbs up to cliff nests, and may be used on nest entries of varying lengths (up to the length of your rope). These ropes may stretch up to 7 — 10% of rope length, making long rappels "bouncy" and prone to dislodging rocks from above and onto the climber and study species. It is best to use 10.5 — 11 mm ropes for most nest entry work; thinner, 8.0 — 9.5 mm, ropes should be avoided even if doubled.

Ropes come in standard lengths of 50, 60, and 70 m, or spools of up to 200 m. Longer ropes provide greater utility for raptor work on cliffs, but are heavier and bulkier. Sometimes, shorter ropes are more appropriate for smaller trees and cliffs for weight, management ease, and swift ascents or descents.

Ropes can be purchased pre-treated to be more water-repellent. These are called dry ropes. Dry treatment lengthens rope life, eases rope handling, and reduces water retained in the rope under wet conditions. Dry dynamic ropes work best for most raptor cliff work, and could be the rope of choice for their versatility. Rope bags are useful for tree climbing, rappelling over brushy or sloping terrain, and when ropes need to be

OCR
Tag: greater hawk knowledge making peregrine raptors

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