Archived 2012-2013 topics: Pulitzer’s Longbill (Macrosphenus pulitzeri): downlist to Vulnerable or Near Threatened?

BirdLife species factsheet for Pulitzer’s Longbill Pulitzer’s Longbill Macrosphenus pulitzeri is known from the escarpment of western Angola. It is currently listed as Endangered under criteria B1ab(i,ii,iii,iv);C2a(i), on the basis that it has a very small, severely fragmented range, a very small population and was suspected to be in decline owing to habitat loss and degradation. However, recent surveys have found the species to be more numerous and widespread than was first thought. It was previously known only from near Seles and Chongoroi (Dean 2000) and was discovered at Kumbira Forest in 2003 (Ryan et al. 2004), but it has since been found to be common in dry forest and secondary growth at Bango and Gungo (M. Mills in litt. 2007, Mills 2010). Mills (2010) states that “its distribution is more-or-less continuous within its range”; implying that the population is not fragmented, as originally thought. It was found to occur over a length of c.370 km of scarp c.10 km wide, and since it can be common in secondary growth, Mills (2010) concluded that the population is almost certainly greater than 1,000 individuals. Remapping of the species’s range has resulted in an estimated Extent of Occurrence (EOO) of c.13,100 km2. This suggests that Pulitzer’s Longbill no longer qualifies as Endangered, on the basis that the population is not fragmented, it is not present in ≤5 locations and its range is larger than previously thought. If there is evidence to suggest that the population is still in decline, this species may warrant downlisting to Vulnerable or Near Threatened. It would qualify as Vulnerable if a) the population is found at ≤10 locations, under criterion B1ab(i,ii,iii,v), and/or b) all subpopulations ≤1,000 mature individuals, under criterion C2a(i) of the IUCN Red List. If these thresholds are nearly met, reclassification as Near Threatened may be more appropriate. BirdLife draft range map for Macrosphenus pulitzeri Subpopulations are defined by the IUCN as geographically or otherwise distinct groups in the population between which there is little demographic or genetic exchange (typically one successful migrant individual or gamete per year or less). The term ‘location’ defines a geographically or ecologically distinct area in which a single threatening event can rapidly affect all individuals of the taxon present. The size of the location depends on the area covered by the threatening event and may include part of one or many subpopulations. Where a taxon is affected by more than one threatening event, location should be defined by considering the most serious plausible threat. (IUCN 2001). For example, where the most serious plausible threat is habitat loss, a location is an area where a single development project can eliminate or severely reduce the population. Where the most serious plausible threat is volcanic eruption, hurricane, tsunami, frequent flood or fire, locations may be defined by the previous or predicted extent of lava flows, storm paths, inundation, fire paths, etc. In order to reassess the status of this species, further information is required on population trends of this species (with any evidence of population declines), the size of the largest subpopulation and species distribution. Comments on the proposed downlisting are welcome. References: Collar, N. J. and Stuart, S. N. (1985) Threatened birds of Africa and related islands: the ICBP/IUCN Red Data Book. International Council for Bird Preservation, and International Union for Conservation of Nature and Natural Resources, Cambridge, U.K. Dean, W. R. J. (2000) The birds of Angola. British Ornithologists’ Union, Tring, UK. Mills, M. S. L. (2010) Angola’s central scarp forests: patterns of bird diversity and conservation threats. Biodiversity and Conservation 19(7): 1883-1903. Ryan, P. G., Sinclair, I., Cohen, C., Mills, M. S. L., Spottiswoode, C. N. and Cassidy, R. (2004) The conservation status and vocalisations of threatened birds from the scarp forests of the Western Angola Endemic Bird Area. Bird Conservation International 14: 247-260.

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4 Responses to Archived 2012-2013 topics: Pulitzer’s Longbill (Macrosphenus pulitzeri): downlist to Vulnerable or Near Threatened?

  1. Michael Mills says:

    We should be careful not to underestimate the threats to the scarp forests and remaining habitat of Pulitzer’s Longbill. While the species does have a greater range than previously thought, its habitat is being cleared very rapidly. At one of the most extensive sites of suitable habitat (Kumbira Forest), there were at least seven pairs during surveys conducted during 2005. In a study of the same area in 2010 (longer and more thorough) there were zero pairs found. So within the best-known area there has been a massive decline in the species in just five years. The species appears to be dependent on dense liana tangles and thickets, both of which are being cleared very rapidly. Post-war development is becoming more and more rapid (fuelled by one of the fastest growing economies in the world) and the situation is likely to have changed quite dramatically since the 2005 surveys. I have not visited Bango since 2009, but massive intensification of agricultural activities in this area was already taking place then and a new tar road passes the site and is likely to lead to even more development.

    Also, could you give a source for the EOO as 13,100 km2? I estimated the range of the species to be 3700 km2 in the 2010 paper.

  2. Joe Taylor says:

    Dear Michael,

    Many thanks for your comments. I have added the draft range map for this species to the forum topic. This is the map from which the new EOO has been derived, and is based on the localities of records and the species’s known elevation range. I do apologise for not posting this sooner. Please let us know if you have comments on the map.

    Joe

  3. Fábio Olmos says:

    I think there is a problem between what is assumed as the range and the actual area occupied by the species. Its habitat (vine tangles in and the edge of the remaining forest patches) is patchy and metapopulations far and away of each other. And, as Ricardo Lima and Aimy Caceres (who have just been in Kumbira forest) report, the area is rapidly being cleared to make room for agriculture to supply the burgeoning market of Luanda. Doesn’t seem a good prospect

  4. Joe Taylor says:

    The following comments were received from Michael Mills on 22 August 2013:

    I don’t think our knowledge is good enough to make even a vague stab at the population size of Pulitzer’s Longbill. We only know three areas of central scarp habitat, and two of those are known from surveys conducted in 2005. At that time the longbills were moderately common at all three sites. However, at the only site we have been monitoring regularly since then (Kumbira), the species has become almost extinct in the main study region, I believe as a result of clearance of dense undergrowth and vine tangles for subsistence agriculture. This is likely to be a distribution-wide trend, as subsistence farming has dramatically intensified since 2005.

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