It is possible, then, that territory improvement and territory shifting as a result of breeding failure act in concert.
At the same time, although territory shift distances seem to decrease during a male's breeding career, their high variation and lack of statistical significance suggests that other factors are at play, such as territory shift after a season of breeding failure.
Hence, the results of the necropsies and egg-content analyses performed (see methods) suggest that pathogens (mainly Salmonella spp., E. coli O-86 and Chlamydophila psittaci) play an important role in breeding failure in the Canarian Egyptian vulture population, which has the lowest known breeding success for this species within its distribution (0.5 fledglings/pair/year, [9]).
As a previous work, after the verification of breeding failure, we developed the analyses of egg content (three unfertile eggs and four embryos) and necropsy of two dead fledglings from Canary Islands.
Because in many species, breeding failure seems to prompt a territory shift, then in the sedge warbler, the decision on a new location to hold should depend on the breeding result in the previous season.
Because heterozygosity has not dropped in parallel with the inbreeding coefficient (Figure 1B) and selection appears to act to maintain heterozygosity (Figure 2B), the calculated figure of breeding failure equivalents is probably an underestimate of the true number of detrimental alleles.
The study of this material did not require of the approval of an ethics committee because it was collected after breeding failure (egg or nestling death) was confirmed in the field.
The results imply that tall wetland vegetation is a long-term, effective environmental cue and that a preference for territories in which this type of landcover prevails has evolved into a rigid behavioral mechanism, supplemented by short-term individual experiences of breeding failure.
We do know that it is very strongly influenced by weather conditions, and we have found in the past that a combination of a warm spring followed by a return to freezing conditions in the incubation period is associated with breeding failure".
Rarely, a very early moult at the nesting colony may be linked to breeding failure, both the onset of moult and reproductive behaviour being linked to falling levels of the hormone prolactin.
