This discussion was first published on Dec 1 2010 as part of the 2010-2011 Red List update.
Initial deadline for comments: 31 January 2012.
Spotted Owl Strix occidentalis is currently listed as Near Threatened under criterion C2a(i), on the basis that its population size is estimated at 15,000 mature individuals (Rich et al. 2004) (which approaches the threshold for Vulnerable of fewer than 10,000 mature individuals), and was suspected to be in decline owing to continued habitat fragmentation, degradation and disturbance through clear-felling and selective logging (del Hoyo et al. 1999), as well as competition from and hybridisation with Barred Owls Strix varia (Kelly and Forsman 2004). In contrast, populations in Mexico are suspected to be stable because of habitat tolerance combined with forestry activities that typically modify rather than destroy habitat (Lammertink et al. 1996, J. M. Lammertink in litt. 1998).
Trend analyses using Audubon Christmas Bird Count data gathered since 1965-66 suggested that this species’s population is not declining, and may even be increasing slightly (Butcher and Nivel 2007). By the 2011 Red List update, this species will have been considered to be stable and possibly increasing in the USA for five years, making it eligible for downlisting to Least Concern, as it does not approach the thresholds for Vulnerable under any of the other criteria. Comments are invited on this potential category change, and further information is requested on this species’s likely population size and population trend, and the current severity of threats.
Butcher, G. S. and Nivel, D. K. (2007) Combining Data from the Christmas Bird Count and the Breeding Bird Survey to Determine the Continental Status and Trends of North American Birds. Washington D.C.: National Audubon Society.
del Hoyo, J., Elliott, A. and Sargatal, J. (1999) Handbook of the birds of the world, Vol 5: Barn- owls to Hummingbirds. Barcelona, Spain: Lynx Edicions.
Kelly, S. G. and Forsman, E.D. (2004) Recent records of hybridization between Barred Owls (Strix varia) and Northern Spotted Owls (Strix occidentalis caurina). Auk 121: 806-810.
Lammertink, J. M., Rojas-Tomé, J. A., Casillas-Orona, F. M. and Otto, R. L. (1996) Status and conservation of old-growth forests and endemic birds in the pine-oak zone of the Sierra Madre Occidental, Mexico. Amsterdam: Institute for Systematics and Population Biology.
Rich, T.D., Beardmore, C.J., Berlanga, H., Blancher, P.J., Bradstreet, M.S.W., Butcher, G.S., Demarest, D.W., Dunn, E.H., Hunter, W.C., Inigo-Elias, E.E., Martell, A.M., Panjabi, A.O., Pashley, D.N., Rosenberg, K.V., Rustay, C.M., Wendt, J.S. and Will, T.C. (2004) Partners in flight: North American landbird conservation plan. Ithaca, NY: Cornell Lab of Ornithology.