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Rare Birds in Spain

Identification and occurrence

The Wilson's Snipes at Tenerife, 2013, 1st for the Canary islands and Spain: some views on its id.

Fernández, R., Barone, R., Larsson, R., Acedo, A. & Pérez, D. 2013

Text edited and compiled by R.Gutiérrez.

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Tenerife bird. 7.11.2013 © David Pérez

Resumen. Las agachadizas de Wilson en Tenerife, 1ª cita para las Canarias y España: algunas notas sobre su identificación. A principios de noviembre de 2013 se da a conocer en el blog Canary Islands Birding News la noticia de la presencia de dos Gallinago delicata en una pequeña charca de Tenerife, aportándose valiosa documentación gráfica. Al hacerse pública la noticia, diferentes ornitólogos insulares y de la Península se acercan a ver el ave consiguiéndose un conjunto de imágenes que, cotejadas con la bibliografía más reciente, refuerzan la identificación de los ejemplares como agachadizas de Wilson, las primeras para las Canarias y España y alejan las dudas expresadas por algunos autores vista la dificultad de identificación del taxon. Se aportan datos preliminares sobre la observación con el objetivo de aportar información que consolide la información y se complementa la entrada del blog Canary Islands Birding News comentando los criterios de identificación apuntados por Reid (2008) en relación a las fotografias publicadas hasta la fecha, sin menoscabo de los trabajos que los autores iniciales de la cita efectuarán.

Introduction

From 17.10-5.11.2013 two Wilson's Snipes were seen and photographed at Charcas de Tejina y Bajamar, La Laguna, Tenerife, Canary Islands (Ramón Fernández, Rubén Barone y Rolf Larsson). A full account in Spanish was published on 6.11.2013 at Canary Islands Birding News blog.

Once the news were spreaded, the same day local birdwatchers visited the area and easily relocated the birds on 6.11 and 7.11 (Antonio Acedo; Eduardo García del Rey). On 8.11 (Antonio Acedo, David Pérez), see photos in David blog here, and on 9.11 they were still around (Juan Sagardía, Óscar Llama, Rubén Cerdeña). On 12.11 there was at least one present (Antonio Acedo).

Identification had been clearly stated by the initial set of authors and the Canary Islands Birding News fellow team, however, some observers doubted on the record because of the difficulties in its identification. To help clarifying these, and before any deeper work is published elsewhere, we present here a partial analysis of the subsequent set of photos obtained in the following days, which gave more opportunities to check the literature, particularly Reid (2008) and Pyle (2008) for the key ID features of this difficult species, already present in the AERC WP bird list but not in the Spanish list.

Criteria and photos

Reid (2008) stated a number of main identification criteria (download the paper linked in the literature below and follow the explanation with it if desired).

The author stated that two or more clear matches with the criteria would become a clear case for the proposed option and that 'any individual which fits either delicata or gallinago in all the following respects should represent a positive identification', despite difficulties in taking good pictures (at least in 2008 standards...). Let's see how they fit the Tenerife birds:

  • Depth of white tips to secondaries

Photo from Ramón Fernández below (figures 1 and 3) and in-flight shots depicted in Canary Islands Birding News entry show very narrow tips to secondaries.

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Figure 1. Tenerife birds © Ramón Fernández, 2013

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Figure 2. Gallinago delicata. Puget Sound Wing Collection. Bird 22403b. ♂.

Compare the Tenerife photo with the wing above, figure 2 (Wilson's Snipe, 22403b, male, Oct from Puget Sound Wing Collection)

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Figure 3. Tenerife bird, detail. © Ramón Fernández, 2013

And again with the Tenerife bird (magnification from figure 1, figure 3). The Tenerife bird does seem to show <2 mm wide edges, or at least, certainly not > 3,5 mm as in gallinago (see below a right wing from a bird in Zuidelijk Flevoland, Netherlands and note wthe average width of white in secondaries). Reid's appendix 1 gives 89,2% of delicata with edges <2 mm and 10,8% with 2-4 mm edges. A 3,8% of european gallinago would show edges < 2 mm.

This character strongly points towards Gallinago delicata for the Tenerife birds.

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Figure 4. Gallinago gallinago. Right wing feathers. Flevoland, Netherlands. 26 october 1995

  • Extent of white on underwing-coverts

As seen in the photo from Tenerife above, the depicted bird does not show any band on lesser coverts nor in median coverts. A hint of band might be present, if any, in the greater coverts. Reid (2008) has an appendix 2 to avaluate the extent of white in underwing coverts of gallinago and delicata on the basis of the presence of bands in the mentioned areas. For the Tenerife combination of small band on greater coverts and no band on median coverts plus no band on lesser coverts, percentages of occurrence within taxa are as follows:

    • gallinago (Europe): 0
    • gallinago (Asia): 0
    • delicata (North America): 22 (36,7%)

Therefore this combination of absence/presence of underwing bars is diagnostic of Gallinago delicata.

  • Pattern of axillaries

Again check figure 3. Reid's appendix 3 defines different patterns of dark and white barring on axillaries:

    • dark bars > white bars
    • dark bars = white bars
    • dark bars slightly < white bars
    • dark bars half width of white bars
    • dark bars third width of white bars
    • dark bars essentially absent

From the categories above, the clear option is dark bars = white bars which is predominant in the whole set of axillaries. The Reid (2008) paper accounts for the following occurrence in the diferent taxa:

    • gallinago (Europe): Predominant across tract 14 (23,4%) / Predominant in whitest feather: 0
    • delicata (North America):Predominant across tract 15 (38,5%) / Predominant in whitest feather: 19 (47,5%)

The Tenerife pattern shown in figure 3 is typical of delicata despite it can be seen in some gallinago. It does not exclude delicata neither gallinago though. Given the whitest feather shows this equal pattern, delicata is the best option though. See also figure 2 and compare with bird in figure 3.

  • Pattern and shape of outermost tail feather

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Figure 5. Tenerife birds © Antonio Acedo, 8.11.2013

The number of bars in the outermost feather is one of the three features to check. In this case, figure 5 give us at least five bars. Checking Appendix 4 from Reid (2008) we have:

    • 2 dark bars or less
    • 3 dark bars – light bars much wider
    • 3 dark bars – light bars even or a little wider
    • 4 dark bars – light bars much wider
    • 4 dark bars – light bars even or a little wider
    • 5 or more dark bars: gallinago 3 (6.1%) , delicata 23 (46.0%)

This pattern is very rare, therefore, in gallinago, and commoner in delicata (see also figure 6). Shape of the outermost feather is also important, being in this case apparently even throughout the feather and with a rounded tip. Of the options in the same appendix 4, this pattern is favoured by 51,2% gallinago and 64,5% delicata, so it is not clear in any sense. Neither is the angle of the dark bars, so all in all tail feather pattern points towards delicata in what we have, particularly the bars, without being decisive in the rest.

  • Width of outermost tail feather

Cannot be calculated from any photo above.

  • Number of tail feathers

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Figure 6. Gallinago delicata. Puget Sound Wing Collection. 17 tail feathers. Bird 2009116, ♂.

The number of tail feathers of the Tenerife birds is difficult to tell from the available photos but figure 3 (left) seems to show c.14 feathers. A photo on the Canary Islands Bird News seems to show at least two missing central tail-feathers but still gives c.14-15 feathers. According again to Reid (2008) less than 12 tail feathers would indicate gallinago for sure, which is not the case. But a count of 14-18 feathers could point out either species. This character, here, is not diagnostic despite average delicata number is 16, which might be the case of at least one of the birds.

  • Supporting criteria

Pattern of breast, mantle and back and overall colour tends towards delicata.

In conclusion, if following Reid (2008) it is clear that the birds depicted in the photographs from Tenerife account for Gallinago delicata, which, if accepted by the Spanish Rarities Committe (CR-SEO/BirdLife) would become the 1st record for the species in the Canaries and Spain. Further works and photos will be published elsewhere.

 

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Figure 7. Tenerife bird. 7.11.2013 © David Pérez

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Figure 8. Tenerife bird. 7.11.2013 © David Pérez

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Agradecimientos/ Acknowledgements

Those contributing with Canary Islands Birding News blog and Rare Birds in Spain for the benefit of bird knowledge in our country.

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References

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Citation
Fernández, R., Barone, R., Larsson, R., Acedo, A. & Pérez, D. 2013. Identification and occurrence. The Wilson's Snipes at Tenerife, 2013, 1st for the Canary islands and Spain: some views on its id.. Retrieved from http://www.rarebirdspain.net/arbsi043.htm 



 

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The Wilson's Snipes at Tenerife, 2013: 1st for the Canary islands and Spain.

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13.11.2013