Tuesday, 15 July 2014

Thick-billed Parrot ‘love-in’

Posted by Francelia Torres and Stuart Marsden

My longest stop in Mexico was a visit to the Pronatura Noroeste (BirdLife partner in Mexico) project on Thick-billed Parrots Rhynchopsitta pachyrhyncha around Madera, Chihuahua. The team, including Francelia Torres, are working on nesting ecology, ranging behaviour and other aspects of the ecology of this Endangered species, work which started in the 1990s by people like Tiberio Monterrubio-Rico, Ernesto Enkerlin Hoeflich, and the current director of Pronatura, Miguel Cruz.


Thick-billed Parrot pair by nest hole in dead Trembling Aspen (Photo: Stu)

The current research is working on several aspects of the species’ ecology, all aimed at stabilising, or hopefully boosting, the numbers of the ‘Cotorra Serrana Occidental’ (as the species is known locally) in the pine forests. These efforts, as with many parrot species, focus on maintaining and, hopefully, increasing reproductive output.

Pine forests of Tutuaca - here the Cotorros nest in huge conifers (Photo: Stu)

Researchers are counting parrots as they arrive at habitual drinking sites. During our visit Eduardo Cort├ęs, a Pronatura biologist, took some high resolution photos of birds arriving at the drinking site, a small waterfall, and could quite easily recognise the white bills of juveniles against the dark ones of adults. This age identification may have useful applications in this population, as it may have with other parrots (see ‘Eyeing up the population structure of Grey Parrots).

A pair looking forward to doing its bit for the survival of the species (Photo: Stu)

They are also looking at feeding ecology. For a species which eats mainly conifer cone seeds, there would seem to be a lot of food in these forests! But a closer look may reveal some more picky selection of trees to feed in, and, possibly, times of the year when food is relatively  
scarce.


Decades of logging has seriously reduced nest hole availability (Photo: Stu)
The main problem, for me, is undoubtedly, the loss of the large conifers through decades of logging. These are the same forests from which the Imperial Woodpecker Campephilus imperialis disappeared. Like many parrots, the availability of large trees with cavities is hugely important. Is the Thick-billed Parrot a colonial nester? Certainly, at the Madera site, nests are in tight clusters centred around stands of large living or dead Quaking Aspens Populus trenudoides, with up to three nests per tree (Monterrubio-Rico et al. 2006).  These congregations certainly feel like colonies, with pairs interacting and bouncing off each other. But at the Tutuaca site, the Cotorras nest in large conifers, Pseudotsuga and Abies, which are not clustered. Pronatura are monitoring a few nests and it will be interesting to see if reproductive output differs between areas where nests are clustered and dispersed.

Above - Nest box positioned in small Pine; 
Below - Manuel climbing to check nest box contents (Photos: Stu)


Designing a strategy for provision of adequate nest holes, be them in large remnant trees or in nest boxes right across the landscape and at minimal cost and management need, may be a priority for research. Forty artificial nests have been in place at Madera since 2008. So far, they have fledged just 45 young parrots (less than 0.2 per nest per year). Although any extra baby parrots are more than welcome, increasing the yield on investment in nest boxes (perhaps around $400 per nest box provision) through better positioning would be good.


The parrot on the right has its wing around the one on the left, which is nice (Photo: Stu)

While logging may have driven down the population over the last century, uncontrolled fires are a very current threat. One such blaze last destroyed tens of nests. In response, Pronatura will place a further 100 nest boxes in Tutuaca and a third site, Papagochi in time for the 2015 breeding season.

At the time of our visit, the Cotorras were winding up for the breeding season. Judging by the behaviour of the pairs, they were looking forward to contributing towards efforts to save the species. Good luck to them and the Pronatura team.


References


Monterrubio-Rico, T.C., Cruz-Nieto, J., Enkerlin-Hoeflich, E., Venegas-Holguin, D., Tellez-Garcia, L. & Marin-Togo, C. (2006). Gregarious nesting behavior of Thick-Billed Parrots, (Rhynchopsitta pachyrhyncha) in aspen stands.  Wilson Journal of Ornithology 118: 237-243.