Guard nests to increase nest success
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 4
Background information and definitions
If populations are reduced to extremely low levels and have low reproductive success then extremely intensive monitoring can be used to ‘guard nests’ and protect them from a range of threats through direct intervention. Due to the intensive nature of this work it is only likely to be viable if there are volunteers available to do it, and the population being monitored is very small.
Supporting evidence from individual studies
A time-series study on nest success of Puerto Rican parrots Amazona vittata in the Luquillo Mountains, Puerto Rico, between 1973 and 1989 (Lindsey 1992) found that the nest success of 71 Puerto Rican parrot Amazona vittata nests was 66% following the instigation of intensive nest monitoring in 1973, compared with an estimated 11–26% success of 19 nests before nest guarding (1955-72) and a predicted 38% success in 1973-80 had guarding not occurred. Threats to nests included the natural deterioration of nest cavities, predation, exoparasites, poor parental care, unviable eggs (replaced with captive-bred eggs), poor growth or unsuccessful fledging of chicks, human intrusion (three nests) and competition from other pairs. Some nests were affected by multiple threats.Study and other actions tested
A small before-and-after study in 1997 on Codfish Island (1,500 ha), New Zealand (Jansen 2005) found that remotely operated detonators successfully scared rats Rattus spp. from kakapo Strigops habroptilus nests on two occasions. In conjunction with intensive trapping and poisoning of rats on a grid system around six nests (see ‘Control mammalian predators on islands’), this ensured that no nests were lost to rats in 1997, compared with potentially unsustainable predation in the years preceding 1997. No adverse effects on kakapos were found.
A study on Codfish Island (1,500 ha), South Island, New Zealand, in 2002 (Jansen 2005) found that 24 kakapo Strigopus habroptilus nests that were monitored by volunteers produced 26 chicks, of which 24 fledged. Volunteers followed a strict set of protocols and reported to ‘controllers’ frequently to ensure eggs survived. The authors argue that reproduction would have been lower without the intensive monitoring that volunteers provided (and which would not have been possible financially with paid staff).Study and other actions tested
A before-and-after study in western Costa Rica (Vaughan et al. 2005) found an increase in a scarlet macaw Ara macau population from 185-225 individuals in 1990-4 to 225-265 in 1997-2003, following the protection of artificial and natural nesting cavities and several other interventions (see ‘Use education programmes and local engagement to reduce pressures on species’, ‘Promote sustainable alternative livelihoods based on species’, and ‘Provide artificial nesting sites’). In 1990-4 the population had been showing a 4%/year decline. This study is discussed in more detail in ‘Increase ‘on-the-ground’ protection to reduce unsustainable levels of exploitation’.