Archived 2014 discussion: Balsas Screech-owl (Megascops seductus): downlist to Least Concern?

This discussion was first published on Dec 8 2010 as part of the 2011 Red List update, but remains open for comment to enable reassessment in 2014.

Balsas Screech-owl Megascops seductus has a moderately small range in west-central Mexico, where it is a fairly common resident. It is listed as Near Threatened on the IUCN Red List because it was thought to have a restricted range that approaches the threshold for listing as Vulnerable (<20,000 km2) combined with severely fragmented habitat or occurrence at approximately ten or fewer locations and a continuing decline in its habitat, population size or number of locations/sub-populations.

However, this species has been mapped by Natureserve/BirdLife International as having an estimated Extent of Occurrence (EOO) of 80,200 km2, hence it does not appear to approach the IUCN thresholds and appears to warrant downlisting to Least Concern. However, if the species has experienced declines over the past three generations (21 years, BirdLife International unpubl. data) approaching 30% it may warrant listing as Near Threatened under the A criterion (population declines). Given its relatively large range size it seems unlikely that this species will have a population approaching 10,000 mature individuals so it would not qualify as threatened or Near Threatened on population size under the C criterion.

Comments on the population trends of this species and its proposed downlisting are welcomed.

Tecolote de Balsas (Megascops seductus): ¿bajar de categoría a Preocupación Menor?

Esta solicitud de información fue publicada por primera vez el 8 de diciembre de 2010 como parte de la actualización de la Lista Roja de 2011, pero sigue abierta a comentarios facilitar la reevaluación en el 2012.

Plazo inicial para observaciones: 31 de enero de 2012.

El tecolote de Balsas Megascops seductus tiene una distribución pequeña en el centro-oeste de México, donde es bastante común durante todo el año. Está clasificada como Casi Amenazado en la Lista Roja de la UICN, ya que se pensaba que tenía una distribución restringida que se aproxima al umbral de consideración como Vulnerable (<20.000 km2), combinada con un hábitat severamente fragmentada o presencia en diez o menos localidades, y una disminución continua en su hábitat, tamaño de la población o el número de localidades o sub-poblaciones.

Sin embargo, según los mapas de Natureserve / BirdLife International, se estima que esta especie tiene una Extensión de Ocurrencia (EOO) real de 80.200 km2, por lo que no parece acercarse a los umbrales de la UICN y por ende parece sugerir su transferencia a la categoría de Preocupación Menor. Sin embargo, si la especie ha experimentado una reducción de población en los últimos tres generaciones (21 años según BirdLife International, datos no publ.) de cerca de 30% se puede justificar su inclusión como Casi Amenazada bajo el criterio A (disminución de la población). Dada el área relativamente amplia de distribución, parece poco probable que esta especie tiene una población tan baja como 10.000 individuos maduros, así que no se calificaría como Casi Amenazada por su tamaño de población bajo el criterio C.

Cualquier comentario sobre las tendencias de la población de esta especie o su propuesta transferencia a una categoría de menor riesgo sería muy bienvenido.

The following document was sent by Pronatura on 16 February 2012: Megascops seductus Pronatura Feb12

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6 Responses to Archived 2014 discussion: Balsas Screech-owl (Megascops seductus): downlist to Least Concern?

  1. Joe Taylor says:

    The following comments were sent by Paula Enríquez on 19 January 2012/Paula Enríquez envió los comentarios siguientes el 19 de enero 2012:

    Referente a Megascops seductus. En 2009 publicamos un ms en Endangered Species Research . . . Esta especie es endémica a la zona del Balsas de México y esta en la categoría de Amenazada. Los bosques secos están entre los ecosistemas más amenazados por las elevadas tasas de deforestación (Ceballos y García 1995, Trejo y Dirzo 2000). Aunque esta especie utiliza diferentes tipos de vegetación en la Reserva de Huautla, los ambientes conservados tuvieron los más altos valores de densidad (Alba- Zúñiga et al. 2009). Considero que también esta especie debería de considerarse como VU.

  2. Joe Taylor says:

    Pronatura have sent a document with information on this species, and it is posted just below the forum topic.

  3. Joe Taylor says:

    The following comments were received from Héctor Enrique Valdez Gómez on 18 July 2013:

    Balsas Screech-owl is limited to a specific geographic distribution and vegetation community. Basically, it’s present all over Rio Balsas basin consisting of river banks and adjacent slopes. If the species has been reported at certain elevations over 1200 m.a.s.l. (Howell and Webb, 1995) is because thorn forest spread along natural corridors and arroyos strongly influenced by dry climate effect mainly on western slopes of Balsas River (INEGI, 2002). Based on this criterion its current distribution (Clements, 2012) should be reconsidered. Consequently, its present geographic range seems to be much more restrictive. Another important aspect that may affect Balsas Screech-owl distribution lies on the voice for the group Megascops. It is not difficult that individuals registered beyond its habitat had been easily confused with Western Schreech-owl, because of the “bouncing-ball” tempos similarities among species and the plasticity in terms of altitude shown by M. kennicottii. Museum specimens played an important role on defining species’ distribution, unfortunately the “quasiendemic” lack of information that characterizes Balsas Screech-owl makes it a complex task to draw conclusions about population trends and ultimately a status suitably assigned for this species. What is behind any effort designed to fulfill basic ecological protocols beyond the species? Depending on the scale of the studies, the answer is not so promising. The Balsas basin is sadly recognized as one of the country’s most violent territories split by at least four opposite drug cartels which boundaries reach the States of Jalisco, Colima, Michoacán and Guerrero. Recently local civic-guards have merged to protect towns form kidnapping and other forms of crime. Accordingly, any fieldwork in the region becomes a monumental perilously activity. Due this situation, economic development or infrastructure present in the region that might jeopardize critical habitat for this species is practically missing and if present, take place into a “parcela” scale (4 – 20 ha). Thus, only local biologist or trained guides may put in practice owl surveys in a very specific portion as extend as their safety can be guaranteed, unless social issues in Mexico improve significantly.

  4. Joe Taylor says:

    Alba-Zúñiga et al. (2009) carried out surveys for the species in Sierra de Huautla Biosphere Reserve and recorded individuals in all five habitat types visited, including conserved dry forest, perturbed dry forest, thorn forest, Gliricidia-Caesalpina forest and agricultural areas. Nova-Muñoz et al. (2011) also recorded the species in secondary growth during surveys of the Tuxpan sub-basin in Guerrero.

    Such flexibility in habitat use and tolerance of modified areas suggests that the species’s population and habitat should not be considered very or severely fragmented, as it is unlikely that the proportion of suitable habitat in patches too small to support viable populations approaches 50%. The species’s use of modified landscapes and secondary habitats also suggests that its population may be buffered to some extent against the impacts of habitat loss and degradation.

    It is also noted that the range map for this species used in its Red List assessment (http://maps.iucnredlist.org/map.html?id=22724664) is in close agreement with the map of potential distribution produced by Navarro and Peterson (2007: http://www.conabio.gob.mx/informacion/gis/layouts/mega_sedugw.png).

    References:

    Alba-Zúñiga, A., Enríquez, P. and Rangel-Salazar, J. L. (2009) Population density and habitat use of the threatened Balsas screech owl in the Sierra de Huautla Biosphere Reserve, Mexico. Endangered Species Research 9: 61-66.

    Navarro, A. G. and Peterson, A. T. (2007) Megascops seductus (tecolote del Balsas) residencia permanente. Distribución potencial, escala 1:1000000. Mexico: Museo de Zoologia, Facultad de Ciencias, Universidad Nacional Autónoma de México and University of Kansas Museum of Natural History.

    Nova-Muñoz, O., Almazán-Núñez, R. C., Bahena-Toribio, R., Cruz-Palacios, M. T. and Puebla-Olivares, F. (2011) Richness and abundance of Birds of the Tuxpan sub-basin, Gerrero, Mexico. Universidad y Ciencia 27: 299-313.

  5. Andy Symes says:

    Preliminary proposals

    Based on available information and comments posted above, our preliminary proposal for the 2014 Red List would be to treat Balsas Screech-owl Megascops seductus as Least Concern.

    There is now a period for further comments until the final deadline of 31 March, after which recommended categorisations will be put forward to IUCN.

    The final Red List categories will be published on the BirdLife and IUCN websites in mid-2014, following further checking of information relevant to the assessments by both BirdLife and IUCN.

  6. Andy Symes says:

    Recommended categorisation to be put forward to IUCN

    Following further review, there has been no change to our preliminary proposal for the 2014 Red List status of this species.

    The final categorisation will be published later in 2014, following further checking of information relevant to the assessment by BirdLife and IUCN.

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