How do I run a carcass persistence trial at a wind farm?
A Carcass Persistence (CP) trial measures how long a bird or bat carcass remains detectable on the ground before scavengers, weather, or decomposition remove it. Without it, every fatality estimate carries an unbounded downward bias that the IFC PCFM Handbook treats as one of the foundational reasons fatality monitoring exists at all:
If a fatality occurs and the carcass is removed or disappears from the search plot before the next search visit, searchers cannot detect it. If the proportion of carcasses that disappear (before searches are conducted) is not estimated and factored into total fatality rates, fatality rates will be biased downward (underestimated).
— IFC PCFM Handbook, §3.3.7.3
How a CP trial runs
- Use fresh or previously frozen carcasses. Real wind farm fatalities are preferred; otherwise use species-appropriate surrogates. Domestic poultry and game birds are scavenged unrealistically fast and should not be used (Box 3.5).
- Mark each carcass discreetly so it is distinguishable from real fatalities.
- Drop from waist height rather than placing directly; record exact GPS location, date, and time.
- Limit to two trial carcasses per turbine at any one time to avoid attracting scavengers and biasing the result high.
- Check on a defined schedule. Days 1, 2, 3, 4, 7, 14, 21, and 30 after placement is standard, with longer windows for raptor-sized carcasses.
- Record status at each check on the CP Trial form (IFC PCFM Handbook Appendix H). Standard minimum evidence that a carcass is still present: two primary feathers attached, or 10 body feathers within a 5 m × 5 m area.
Where to run trials
The IFC PCFM Handbook is direct that trial placement matters as much as schedule. Concentrating trials at one turbine attracts scavengers and biases the persistence rate high:
Carcass placement should be limited to a maximum of two trial carcasses at any one turbine at any one time to avoid undue attraction of scavengers.
— IFC PCFM Handbook, §3.3.7.3