Assessing the impact of removal scenarios on population viability of a threatened, long-lived avian scavenger

The removal of eggs or chicks from wild populations to create captive populations, reinforce free-ranging populations or reintroduce species into the wild is a restoration tool that requires an assessment of potential detrimental effects upon the donor population. This is an absolute prerequisite when wild donor populations are scarce and small. Here, we forecast the population trend of the largest European population of the bearded vulture (Gypaetus barbatus) over the next 30 years under different demographic and management scenarios (removal of eggs, chicks or fledglings). Projections derived from the combination of a PDP model (Population Dynamic P-system) and a Box-Behnken design would lead to a decline in 77% of all 57 scenarios analysed. Among the 13 scenarios predicting a population increase, only 4 seem realistic in terms of growth rate (0.04%–1.01%), at least if current age at first breeding and productivity would remain constant over time. Our simulations thus suggest that most extraction scenarios would have detrimental effects on the demography of the donor population. Release of captive-born young or removal of only the second hatched chick for subsequent captive rearing and translocation into the wild appear to represent much better supplementation and reintroduction options in this threatened species.

module is a step in the model, the complete execution of the loop is eight steps that correspond to a period of one year. Below we describe the rules that apply to each of the eight steps. The parameters used in the model rules appear in Table S1.
Step 1. The central process is natural mortality, although the aim of the first rule is to generate objects that subsequently allow monitoring of the maximum density of animals in the area.
The objects will allow for the control of the maximum load, while objects are used to generate randomness in population size. 1 is a counter that evolves at each step and is used to synchronize the model. According to the probability of death that depends on the age of the individuals, the same objects evolve while others disappear, if the animal dies.
Step 2 The central objective of this step is to start the process of reproduction with egg laying; as occurred in the first step here are applied in parallel rules unrelated to the process of reproduction, such as rules 11 and 12.These rules generate the model randomness in the final population size after reaching maximum density, the 50% objects type are dissolved while the remaining objects type a evolves.
The objects associated with individuals of reproductive age that breed successfully generate news objects, EG representing laying eggs. The objects associated with animals evolve to objects .
Step 3 Nest interventions: Clutches There are many objects as nests intervened.
Step 4 Hatching success Clutches can be double but only a chick can complete the process successfully; we can thus establish the relationship of one egg for each laying. Some of the eggs will hatch ( ), which generated hatched objects 0 associated with new individuals entering the inner membrane labeled with the value 1.
All other objects associated with bearded vulture also come into the inner membrane, as well as the and objects. These objects store information of the interventions. If objects left over are dissolved because its function has ended.
Step 5 Nests intervention: chicks in the nest The number of intervened nests is , the removed chicks at nest will disappear.
The object that will allow modeling fledgling interventions evolves as not consumed, the purpose of the evolution of this object is to prevent the rules of intervention for the fledglings are applied in the wrong time.
Step 6. Several of the hatched chicks abandon the nest successfully. The central objective of this step is to model the fledglings.
In parallel to the process of fledglings are applied rules that increment by one the age of the animals while controlling maximum carrying capacity.
Step 7 Fledglings Fledglings as there are objects ′ of the type are extracted, these fledglings disappear ecosystem.
Unconsumed objects will be dissolved Evolution objects that are associated with the vulture, this evolution allows objects not start the cycle prematurely Step 8 Update Restoring the original configuration, the system is prepared to start the simulation of the following year, i.e., restart the loop.

Density-dependent model (DDM)
The proposed PDP model is structured in four sequenced modules: mortality, count number of adult animals, reproduction and restore initial configuration.
Step 1 Generation of objects for controlling the maximum load and mortality For each adult that survive it's generate one object type Step 2  Step 15 maximum load control and preparing to start playback settings Step 16 Reproduction rules Step 17 Restore initial configuration  probability that a pair in reproductive age start laying probability that a egg hatch with success probability that a hatched chick abandon the nests successfully removal of eggs ℎ removal of chicks removal of fledglings year 1 when exist intervention and 0 when not intervention take place maximum productivity minimum productivity ______________________________________________________________