{'fraction_non_alphanumeric': 0.01435670900055218, 'fraction_numerical': 0.006626173384870237, 'mean_word_length': 5.019933554817276, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
An Empirical Simulation Model of an Avocet Recurvirostra avosetta Population

An empirical simulation model of an Avocet population was constructed using a k-factor analysis from 40 years' data. The model was tested with an independent data set and then used to evaluate the effects of manipulating egg loss and chick loss on breeding pair density and productivity. Model predictions of pair density and density of fledged young were similar to observed data. When values for chick loss from an independent population were substituted in the model, predictions of the independent population were also very close. Manipulation of egg loss had little effect on (a) pair density, (b) density of fledged young, and (c) overwinter loss. Manipulation of chick loss had a large effect on pair density until 1969 when overwinter loss changed from being weakly density dependent to being almost perfectly density dependent. From 1970 onwards manipulation of chick loss had little effect on pair density. Manipulation of chick loss had a large effect on the density of fledged young and on overwinter loss for the 40 year period. The model suggests that the decline in the number of young fledged per pair observed on the study site was due largely to the increase in chick loss over the period. Density dependent egg loss played no role. The management implications of the model are that breeding populations cannot be increased significantly by manipulation to reduce either egg loss or chick loss. Management to increase chick survival would, however, increase productivity thereby creating a cohort of dispersers which could colonise other sites an important conservation objective. The role and importance of immigration and emigration should be investigated by a comprehensive marking study over a long time period.