Regurgitated pellets are often difficult to find and their collection requires a lot of time.
Is is better to collect them as much as possible and to assess the quality of the sampling at
the end, using a richness estimator, rather than to establish a preliminary statistical
sampling. To study feeding ecology, parameters such as the date of collect, sex and age,
reproductive phenology, location and description of their habitat, etc., are simultaneously
collected.
There does not exist any specific key for pellets determination in insectivorous birds
because their morphology depends on what the birds eat. A particular attention must be
given to the other insectivorous bird species which occur in a given study area. As for
pellets, there does not exist any specific key determination for remains of prey. The
establishment of a reference collection, including as much as possible of the potential prey,
is necessary to distinguish the closely related species.
Biomass of the potential prey can be measured directly in the field with a precise
weighing machine. In the case of desert species, it is better to talk in terms of wet biomass
rather than in terms of dry biomass because water is obviously essential. The best is to
measure water composition by calculating the difference between wet and dry biomass.
The energetic and nutritional values can only be measured in a specialized laboratory.
Finally, some kinds of prey are not easily perceptible and their detection often requires
the use of a special material (for example, the cuticle of Scorpions is detected with an
ultraviolet light).
Is is better to collect them as much as possible and to assess the quality of the sampling at
the end, using a richness estimator, rather than to establish a preliminary statistical
sampling. To study feeding ecology, parameters such as the date of collect, sex and age,
reproductive phenology, location and description of their habitat, etc., are simultaneously
collected.
There does not exist any specific key for pellets determination in insectivorous birds
because their morphology depends on what the birds eat. A particular attention must be
given to the other insectivorous bird species which occur in a given study area. As for
pellets, there does not exist any specific key determination for remains of prey. The
establishment of a reference collection, including as much as possible of the potential prey,
is necessary to distinguish the closely related species.
Biomass of the potential prey can be measured directly in the field with a precise
weighing machine. In the case of desert species, it is better to talk in terms of wet biomass
rather than in terms of dry biomass because water is obviously essential. The best is to
measure water composition by calculating the difference between wet and dry biomass.
The energetic and nutritional values can only be measured in a specialized laboratory.
Finally, some kinds of prey are not easily perceptible and their detection often requires
the use of a special material (for example, the cuticle of Scorpions is detected with an
ultraviolet light).
Wing and forewing of Rattle Grasshopper
Psophus stridulus stridulus
Psophus stridulus stridulus
