Two experimental nest-box trials were attempted, which aimed to maximize uptake by Marsh Tits in British woodland. Nest-boxes which more closely approximated the dimensions of natural cavities were used more frequently than standard nest-boxes, but the overall uptake was low. We conclude that nest-boxes are an inefficient method of monitoring Marsh Tits, at least in the British context, and researchers should concentrate efforts on locating and monitoring natural nest-sites.The Marsh Tit is a small (10-12 g) woodland passerine which nests in secondary treecavities (Broughton et al. 2011), and its abundance in Britain declined by 73% from 1967-2011, placing it on the Red List of birds of conservation concern (Baillie et al. 2014). Consequently, monitoring of demographic trends has become more urgent, including breeding success and productivity. However, Marsh Tits are infrequent users of nest-boxes (Perrins 1979), which are the most efficient means of monitoring breeding parameters, particularly for 'citizen science' projects such as the BTO's Nest Record Scheme. The reasons for this low uptake are unknown, but may include nest-box competition from dominant Blue Tits Cyanistes caeruleus and Great Tits Parus major, a preference for different cavity properties than offered by standard nest-boxes, or microhabitat selection around nest-sites (Broughton et al. 2012). The aim of this paper is to report on two experimental nest-box trials which aimed to use information on territory location, nest placement and natural nest-sites to maximize nest-box uptake by Marsh Tits. If successful methods could be applied more widely, then this would facilitate nest recording and ringing of nestlings for improved population monitoring. Since 2003 we have studied Marsh Tits in the 155 ha Monks Wood National Nature Reserve in Cambridgeshire, eastern England (52° 24' N, 0° 14' W), and neighbouring woods within 5 km, including aspects of nest-site selection and nest placement in natural cavities. Each year at least 80% of the Marsh Tit population was marked with individual combinations of colourrings, all birds were sexed according to behaviour and biometrics, all breeding territories were mapped, and 200 nests were located up to 2014 (see Broughton et al. 2008Broughton et al. , 2011Broughton et al. , 2012 for details). The study woods were largely unmanaged ancient woodland, dominated by Common Ash Fraxinus excelsior, English Oak Quercus robur, Common Hazel Corylus avellana and hawthorns Crataegus spp.. In December 2003 we began a nest-box trial aimed at improving occupation by Marsh Tits, using nest-boxes approximating the standard 'small hole-entrance' design recommended by du Feu (2003). Boxes were erected in pairs at 15 locations in previous Marsh Tit breeding territories, close (< 10 m) to recent nest-sites where possible (five locations), with inter-box distances of 3-5 m to leave a nest-box available for Marsh Tits should one be taken by the dominant and common Blue Tits (Nilsson & Smith 1988).
Page 1 of 8Nest-boxes were...