Methods
For the purposes of this review, we followed the definition of
waterbirds used by Wetlands International (2012). This covers all
species within 32 bird families that are ecologically dependent on
wetlands. The most familiar of these families are the Anatidae (ducks,
geese and swans), Laridae (gulls and terns), Ardeidae (herons and
egrets), Scolopacidae (sandpipers), and Charadriidae (plovers). Other
representatives include the Rallidae (rails and crakes), Podicipedidae
(grebes), Threskiornithidae (ibises and spoonbills), and
Recurvirostridae (stilts and avocets).
Systematic reviews require defining the question elements ‘subject’,
‘intervention’, ‘outcome’, and ‘comparator’ (Pullin and Stewart, 2006).
The diverse nature of the waterbird habitat quality literature meant
that many waterbird habitat quality studies lack one or more of these
elements (e.g., most studies are descriptive rather than measuring the
outcome of a management intervention relative to a control case).
Consequently, conducting a formal meta-analysis was not possible. Hence,
we used the ‘narrative synthesis’ approach recommended by Haddaway et
al. (2020) for synthesising heterogeneous literature. To obtain a
representative sample of the literature for synthesis, we used a
structured approach to identify relevant information sources (published
literature, reports, and grey literature) and use these sources to make
qualitative assessments of the various methods that have been used for
measuring waterbird habitat quality.
We searched the Web of Science (all databases) on 17 December 2020 to
obtain a set of papers on which to base this review. The following
search string, in which TS means ‘Topic Search’, was used:
TS = (waterbird* OR shorebird* OR wader* OR ”wading bird*” OR waterfowl)
AND TS = (”habitat quality” OR ”habitat condition” OR ”environment*
quality” OR ”environment* condition” OR ”wetland quality” OR ”wetland
condition”)
This returned 411 search results (398 after removing duplicates) upon
which the following synthesis is based (See Table S1 for list of
returned results).