TABLE 1.

Examples for studies with a similar study design, analyzing the abundance and diversity of cavity‐nesting Hymenopterans, carried out in different Western European countries

Reference	Country	Landscape	Sites	Trap nests	Reeds	Sampling period	Most abundant taxa
Albrecht et al. (2007)	Switzerland	Grassland	13	8	ca. 200	April–October	Trypoxylon figulus
Steffan‐Dewenter (2002)	Germany	Agricultural	15	8	150–180	April–October	Osmia bicornis (rufa); Hylaeus communis
Diekötter et al. (2014)	Germany	Agricultural	12	2	NA	March–October	Osmia bicornis (rufa)
Fabian et al. (2013) and Fabian et al. (2014)	Switzerland	Agricultural	12	14	170–180	April–October	Osmia bicornis; Trypoxylon figulus; Ancistrocerus nigricornis
Gathmann et al. (1994)	Germany	Agricultural	40	6	180	April–October	Megachile sp.; Osmia sp.; Trypoxylon sp.
Happe et al. (2018)	Germany	Agricultural	36	2	NA	April–September
Holzschuh et al. (2009)	Germany	Agricultural	12	5	ca. 200	April–September	Trypoxylon sp.; Symmorphus sp.
Holzschuh et al. (2010)	Germany	Agricultural	46	2	150–180	April–July	Osmia bicornis (rufa)
Krewenka et al. (2011)	Germany	Grassland	55	216 (total)	ca. 200	April–October	Trypoxylon sp.; Passaloecus sp.
Kruess and Tscharntke (2002)	Germany	Grassland	18	4	150–180	April–October	Trypoxylon figulus
Schüepp et al. (2011)	Switzerland	Agricultural	30	2	ca. 170	April–October	Trypoxylon figulus; Osmia bicornis
Sobek et al. (2009)	Germany	Woodland	12	12	NA	May–September	Ancistrocerus trifasciatus; Trypoxylon clavicerum

We distinguished three different groups of studies according to the main characteristic of the landscape around the study sites in these studies (=agricultural landscape, grassland, woodland). The number of sites, trap nests per site, reeds (Phragmites australis Cav.), the sampling period, and the most abundant taxa reported in these studies are also given. The reed diameters, if reported, ranged from 2 to 10 mm in almost every case.