Archived 2010-2011 topics: Are São Tomé’s pigeons more threatened by hunting than current Red List status suggests?

Link to BirdLife species factsheet for Maroon Pigeon

Maroon Pigeon Columba thomensis , São Tomé Bronze-naped Pigeon Columba malherbii and São Tomé Green-pigeon Treron sanctithomae are all endemic to the islands of São Tomé, Príncipe and Annobón. Maroon Pigeon, currently listed as Vulnerable under criterion D1, occurs only on São Tomé as does the Least Concern São Tomé Green-pigeon, while the Least Concern São Tomé Bronze-naped Pigeon occurs on São Tomé, Príncipe and Annobón.

A major threat to all three species is uncontrolled hunting with the bushmeat trade potentially having a negative impact on populations. Maroon Pigeon has an estimated population size of 250-999 mature individuals but it is assumed to be stable. If declines owing to hunting pressure are now evident the species may warrant uplisting to Endangered under criterion C2aii of the IUCN Red List criteria owing to its declining population of <2,500 mature individuals confined to a single population. If the population of São Tomé Green-pigeon and/or São Tomé Bronze-naped Pigeon now approaches 10,000 mature individuals and declines are evident owing to hunting pressure these species could also qualify as Near Threatened (if >10,000) or Vulnerable (if <10,000) under criterion C2aii. Alternatively the species may qualify if declines approach the thresholds under criterion A, i.e. 30% over three generations (12.7 years based on a generation time of 4.2 years, BirdLife International unpublished data).

Comments on these potential category revisions are welcomed, particularly estimates of population size and rate of decline for these species.

(This discussion was first started as part of the 2010 Red List update)

The following figures were submitted by Ricardo Faustino de Lima on 27 January 2011 (not BirdLife data):

C. malherbi: This is a favourite quarry species often sold in bars and parties (Ricardo Faustino de Lima in litt. 2011)
T. sanctithomae: Several hunters visit the more sparsely inhabitaded parts of the island in order to get larger numbers of this species. Allegedally it has become less common in the North of the island, which is not surprising given that it is a rather tame bird (Ricardo Faustino de Lima in litt. 2011).
Distribution of the endemic pigeons of Sao Tome – Each sampling location is marked by a small dot. The frequency of each species is represented by the size of a shape representing land-use type: circle – old growth forest; square – secondary forest; triangle – shade plantation; losange – other agricultural land-use. The maps on top represent the total number of times the species was present (in 3×5 point counts), while the bottom ones represent the number of times in which the species was present at less than 20m from the point).

Related posts:

  1. Archived 2010-2011 topics: São Tomé Thrush (Turdus olivaceofuscus): list as Near Threatened?
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6 Responses to Archived 2010-2011 topics: Are São Tomé’s pigeons more threatened by hunting than current Red List status suggests?

  1. Andy Symes says:

    Fabio Olmos has provided the following input:
    29 September 2009
    “All pigeons are intensively hunted and it seems hunting, not ecology, determines the current distribution of the Maroon Pigeon. Which is scarcer than currently recognized threatened species. In January 2008 I saw only 1, compared to 7-8 Dwarf Ibises… All hunters also point Green Pigeons are now harvested in numbers below half they used to be. My opinion? Maroon pigeon is En and the Green Pigeon Vu.

    Utilisation of Pigeons_Relatório Mariana Caça1.pdf

    Mariana Carvalho provided the following information:
    29 September 2009
    I believe that all the three species of pigeons (Columba thomensis, Columba malherbii and Treron sanctithomae) are misclassified for their conservation status, as all the three are strongly harvested and apparently have distributions affected by hunting patterns and pressure. I have five months of distribution and abundance data for all the columbidae which I will analyse and share soon. I also have contact with bird hunters and I will be working with them to get more data on the birds biology and ecology. Anyway, Maroon Pigeon is far more threatned than “vulnerable” and is getting rarer, even at higher altitudes. Both C. malherbii and T. sanctithomae are also becoming more and more difficult to sight at more populated places.

    4 February 2010
    I am sorry for the late reply. In fact, I was trying to get some results to contribute to the discussion still this year, but I am facing strong evidences of seasonality of the birds, which make me think it will be safer to pronouce about it next year. I am collecting monthly data on the three columbidae endemic species in five 5kms transects in all forested habitats and now another 10 1km transects, around the island. I know that next year I can provide some consistent data, but at the moment I want to improve the sampling to be sure of the results.

  2. Fabio Olmos says:

    I spent a fdew days in Sao Tome last August, what allowed me to revisit places I surveyed two years before. Considering the harvest levels and perceived decline in numbers my opinion is Maroon Pigeon deserves EN status, while Green Pigeon easily fits VU based on the perceived decline in numbers sighted in places like Lagoa Amelia and Monte Carmo. I don´t have much info on C. malherbii because so few were seen, what gives you a cllue they may be in trouble.
    Bushmeat exploitation is an issue, not only for subsistence but also comercial enterprises. For example there is a notorious restaurant run by a catholic priest offering bushmeat-fed parties every week (it is supposed to create ties in the community….), the guy supplying ammunition to the hunters.

  3. Quite close to the deadlines to post this forum, I would like to contribute to the discussion on the status of the three fruit Columbidae form São Tome island, Maroon Pigeon (Columba thomensis), ST Green Pigeon (Treron sanctithomae), and the Bronzed Naped Pigeon (Columba malherbii). I have collected information on these birds’ abundance and distribution for 13 months, together with data about hunting pressure and fruit ecology, and I believe they should all change status for a higher one.

    I believe that the Maroon Pigeon should be reclassified as Endangered, following the RL criteria: there are no references to compare with actual values of abundance and distribution, but there are strong indications that the population of the species is declining, both in numbers as in the area of occurrence and occupancy, mainly due to the hunting pressure over the bird, which has not stopped or reduced for the time being. A maximum of 18 birds was observed in two 1km transects after the breeding season in primary altitude forest (near the Pico of Sao Tome, the core area of the species), roughly representing an average of 0,45 birds/ha. For the area of Lagoa Amelia and surroundings, an average of 0,108 birds/ha was observed during the 13 months of data collection, along 5 kms of suitable habitat.
    On the other hand a single hunter in just one session killed 9 birds (including 3 mature adults, 1 male and 2 females, and 6 juveniles and immature) in a feeding habitat for the pigeon, and repeated these sessions as long as he could found a bird to kill. Also, the evidences of hunting are huge whenever the bird shows up close to people, or in specific identified feeding places, where several cartridges and hunting signs were observed. The preliminary analysis of the seasonal patterns of its distribution relate the movements with fruit availability, with incursions in lowland forest but also secondary and shade forest. Though, due to the accessibility of these two habitats, and the empiric knowledge of hunters of the feeding places, the actual frequencies of the Maroon Pigeons in the generality of these areas are almost null.

    The ST Green Pigeon is also being clearly affected by hunting pressure, and it reflects on the birds’ actual distribution. In the census, the average number of birds observed was three times higher in primary forest (both altitude and lowland), than in secondary or shade forest. This suggests that there is a reduction on the area of occurrence and occupancy promoted by a strong hunting pressure over the species, which has not stopped or reduced, and it is much stronger in accessible habitats (as it can be caught with a simple slingshot or air pressure weapons, much cheaper than firearms). Adding the present information with historical references of a widespread distribution and high numbers of birds (see Jones and Tye, 2005), and the hunters records of the double of captures only five years ago, I believe that the species should be reclassified as Vulnerable. Also because this is an endemic species of São Tomé island only.

    The Bronze Naped Pigeon is a more complicated because it is strongly seasonal. It is very conspicuous during the breeding season, from November to February, where it sings and shows up in almost all forested habitats of the island but also savannah and coastal areas. During the dry season, though, it almost “disappears” (corroborating what Fabio said in his last post, as he was here in August), and the observations decline considerably from May to October. Even that it is a widespread bird, and still a reasonably common one, it also suffers from a strong hunting pressure, especially during the breeding season, where it is hunted but also collected as juveniles to breed at home (most of the times not successfully, as it is fed basically with corn), and adults to keep in cages and sell as living birds. It is a delight searched by a bunch of restaurants in main cities. Due to the constant (and possibly increasing, as one of young boys hobby is many times its collection and hunting) pervasive threat posed by hunting, the difficulty of estimation of its actual density, but also the fact that it is a species also present in Principe and Anobom, I believe it should be reclassified as Near Threatened.

    Ref. Jones, P. and A. Tye (2005). The birds of Príncipe, São Tomé and Annobón, and annotated checklist. British Ornithological Union nº22

  4. Andy Symes says:

    Please see further information provided by Ricardo Faustino de Lima on Sao Tome endemics in the discussion on Sao Tome Thrush

  5. According to the data I’ve collected in the last two years (see above maps, but also the post about the Sao Tome thrush – http://www.birdlife.org/globally-threatened-bird-forums/2010/12/sao-tome-thrush-turdus-olivaceofuscus-list-as-near-threatened/), I believe that these species are indeed more threatened than what it is currently recognized by the IUCN Red List. The main threats being hunting pressure coupled with habitat loss. Given that the Sao Tome forests are very poor in big fauna, these birds are more likely to become hunted than they probably would in other contexts. On top of all this, the human population is growing very fast, leading to increased pressures not only on the species but also on their habitats.
    The Maroon pigeon (Columba thomensis) is the biggest pigeon and it is also very tame. It seems to have been historically pushed into the most rugged and higher terrains by human pressure. In less visited areas, some birds (probably most of them juvenile) might visit plantations, but they don’t breed here (Jones & Tye 2006). Despite the difficulty of finding this species, some hunters manage to collect rather high numbers of them with a single day in the forest. I think that this species qualifies for Endangered under the criteria B2a,b(iii), C1 and C2a(ii). Additionally it would qualify as Vulnerable for A2c,d.

    The bronze-naped pigeon (Columba malherbi), unlike most endemics, seems to tolerate and even prefer more degraded habitats (Fig.1 in the Sao Tome thrush discussion). Such preference makes it more easily available for hunters, that don’t need to go into the forest to collect them. This species also has a rather strong and hard to interpret seasonality, that makes it hard to make population estimates. It can be quite abundant, usually in large flocks concentrating in fruiting trees. It is a quarry species often available in specialized bars or in parties. It might qualify for Vulnerable under the criteria C2a(ii) or even for Endangered under B1a,c if there is continuing decline. Given that this species also occurs in the nearby island of Principe and Annobon, it would be more correct to classify it as Near Threatened.

    The green pigeon (Treron sanctithomae) is a rather common species in the forests and in less visited plantation areas, when food is available. Large numbers can be seen feeding on fruiting fig trees. However the species is nearly absent from the Northeast, the most populated part of the island. This species is caught for consumption in rural communities and by commercial hunters to sell to specialized bars in the vicinities of the capital. Some commercial hunters can kill large numbers of these birds in one morning. I believe it qualifies for Vulnerable under the criteria A2c,d and C2a(ii). Eventually it can become Endangered under the criteria B1a,b(iii), if it is shown that in fact there is a continuing decline of the species.

    Jones, P. & Tye, A. (1988). A survey of the avifauna of São Tomé & Príncipe. ICBP Study Report 24. ICBP, Cambridge, UK.

  6. Between May and July 2008 I conducted field work for my MSc thesis (on the impact of agriculture intensification on São Tomé’s avifauna) in the area surrounding Lagoa Amélia and agricultural matrix around Monte Café and despite two and a half months of fieldwork with systematic visits to the areas’ shape plantations, horticulture plots and rainforest I did not observe any Maroon Pigeon. In fact, the only live C. thomensis I managed to observe during my stay in island was when, togheter with Mariana Carvalho, I had the chance to follow a hunter on a hunting trip – just on one morning the hunter managed to harvest roughly 30 São Tomé Green-pigeon Treron sanctithomae (some other 30 more were wounded but ended up not being collected) a few C. malherbii and one C. thomensis.

    I fully support Mariana, Fabio Olmo and Ricardo’s position that the current conservation status of the 3 species does not reflect their current situation and, in accordance with the arguments here presented by Mariana and Ricardo I believe that the Maroon Pigeon’s status should be raised to EN, the São Tomé Green-pigeon should be classified as VU and the São Tomé Bronze-naped Pigeon as NT.

    Rocha, Ricardo (2008). Birds in humanized landscapes: São Tomé endemic birds’ response to agricultural intensification. Available at: http://www.iccs.org.uk/thesis/consci/msc08-rocha,ricardo.pdf

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