Conclusions
This review of the literature comprising almost 400 articles strongly
suggests that there is no one broadly accepted method for assessing
waterbird habitat quality. Directly measuring breeding success and
survival rate are the most reliable measures, but it is unfeasible to
obtain these data in many cases. A variety of proxy measures are
available, but their interpretation requires substantive
contextualisation and a good understanding of their appropriateness to a
specific project aim.
In general, if it is not possible to measure direct demographic
parameters, projects should consider the suite of available proxy
measures (Table 1) and consider which are most suitable to their site,
budget and timeframe. Often, developing a protocol based on multiple
proxies will increase confidence in results over the use of a single
proxy. For example, studies investigating the comparative habitat
quality of multiple sites could use a combination of waterbird
abundance, behaviour and body condition coupled with a measure of prey
availability to gain insight into which site(s) are providing better
food resources. Studies assessing if a single site is profitable for
waterbirds from an energy perspective (i.e. habitat quality is
sufficiently high to support population growth) could use a combination
of waterbird behaviour and available energy density to assess whether
daily energy requirements are being met at the site. All studies using
proxy measures should be mindful of the potential for interactions
between features of the habitat (e.g., prey abundance and prey
accessibility) to influence the direction of the relationship between
habitat conditions and resultant demographic rates.