Secondary shrubby communities provide nesting habitat for birds in a semiarid agricultural landscape

Loss and fragmentation of natural and semi-natural vegetation caused by agricultural intensification are related to many declines in shrubland bird populations, but they have received little conservation attention and research effort. In the Llanos de Ojuelos, a semiarid agricultural landscape in Mexico, patches of natural shrubland and nopal (or prickly pear) Opuntia spp. orchards harbour 60% of the regional avifauna, but prior to this study their value as nesting habitat for birds has not been assessed. In 2014 we recorded 143 nests of 25 species, 45% of which were of Mourning Doves Zenaida macroura. The nesting birds recorded account for 38% of all species known to use these habitats in this region and the number of nesting species is larger than in other North American semiarid and arid shrublands. Shrublands and orchards were not different in any habitat attributes measured, nor in the densities of nests found in them, but there were significantly more species nesting in shrublands. Nest height and visibility were not different between habitats, except for Mourning Doves, which nested at a lower height in orchards. Neither attribute affected nest success, except for in Black-chinned Sparrow Spizella atrogularis for whom successful nests were less visible. The assemblages of nesting birds might be explained better by particular plants used as nest substrate than by habitat attributes. Catclaws Mimosa aculeaticarpa var. biuncifera, Huisaches Vachellia farnesiana and V. schaffneri and nopal plants supported 56% of all nests, the latter being particularly important for Mourning Doves, while scarce Central-Mexico Yucca Yucca decipiens trees supported 40% of nesting species. There were interspecific differences in the phenology of nesting, which matched the feeding requirements of the young. Nopal orchards seem to provide abundant complementary food for birds that nest in shrubland patches. Nopal orchards and shrubland patches dotting the landscape may make the dominant agricultural matrix of the southern part of the Central Plateau of Mexico less detrimental to shrubland birds. Our study supports the idea that small patches of secondary shrubland can aid in biodiver- sity conservation in anthropized landscapes, a role that in this region is provided by shrubland remnant patches as well as nopal orchards.