Bird topics

HO107 Angrier in the middle? Does territorial aggression differ with elevation and competitors in tropical understorey passerines?

(start dates 07 June, 14 June or 21 June; need to complete HO001)

Range patterns of species on tropical mountains are generally typified by narrow elevational distributions, particularly in birds, but little consensus as to the exact causes of these distributions has been reached. Physiological stress, ecotones (e.g. habitat and temperature) and aggression between related species may restrict these distributions, but it remains unknown as to whether birds are subject to greater territorial pressures within or at the edges of these elevational ranges as a result. Several species that are suitably abundant and of which the elevational ranges are sufficiently understood, offering ideal subjects for which to study aspects of territoriality, are present in Cusuco National Park, Honduras (e.g. black-headed nightingale-thrush, Catharus mexicanus, and grey-breasted wood wren, Henicorhina leucophrys). A range of projects are possible using playback experiments to assess differences in intraspecific aggression with elevation and local climate regimes and whether interspecific differences occur in range overlaps. This project will complement work currently being undertaken on the role of physiology and aggression in defining the elevational distributions of tropical cloud forest species, focusing on Catharus nightingale thrushes.

Extended Project Summary


HO108 Factors affecting bird communities in the cloud forests of Cusuco

(start dates 07 June, 14 June or 21 June; need to complete HO001)

Birds are excellent indicators of forest ecosystem health as their abundance and diversity are closely related to habitat disturbance and they make ideal models because they are relatively easy to monitor and study. This topic takes advantage of the existing fixed point count survey work being undertaken for birds at over 130 survey sites across Cusuco, as well as the recently started mark-release recapture mist netting survey data. By examining species distributions and species richness across varying habitats, projects could: compare bird communities in different administrative divisions of the park (e.g. the buffer/core zones that differ in degrees of wildlife preservation and human activity); study the impact of differing disturbance levels on bird communities; investigate the impact of habitat type on bird community composition; or look at the effect of altitude on bird composition. By using covariates such as temperature, habitat structure and forest type, threshold limits for the different species could be elucidated which may have interesting implications for the impact of habitat alteration (e.g. by deforestation) in the future.

Extended Project Summary

 

IN121 Island birds as a method of studying evolutionary mechanisms

(start date 20 June; need to complete IN001)

This is a specialised team led by academics studying how bird species and communities change in a series of offshore islands in SE Sulawesi. One student working with this team in previous years was assessed to have produced the best undergraduate dissertation in the UK from her project. The team will be visiting the mainland of SE Sulawesi, Muna, Wowoni and Manui Islands, mist netting birds and gathering detailed morphometric measurements, as well as recording the calls and how they differ between islands. Data gathered on this specialist expedition, together with that from previous similar studies by this team on other islands in the region as well as the mainland, will allow some interesting evolutionary questions to be asked. For example in sexually dimorphic species such as sunbirds and flowerpeckers, there may be some difference in diet between the sexes because of small differences in bill size and shape. If this is correct then it would be expected that at high densities where food resources are limited, that sexual dimorphism would increase the range of resources being exploited. Another study could look at how the black-naped monarch, which is a bird that lives permanently in populations on small islands, varies between islands, compared to the ‘supertramp’ Island Monarch which continually interbreed between islands. Another project could look at the possible existence of cryptic species amongst the widespread grey-capped emerald dove or amongst the abundant munias – the Wallacea version of Darwin’s finches. This team have previously described both a cryptic subspecies and a cryptic species from nearby islands, so the potential for further new species to be discovered there is very real. Given that data on the abundance of food (insects, flowers, fruit), together with density estimates of bird species exploiting those resources, has already been collected by this team from a number of islands in the region, adding similar data from these new islands would give a large data set that could be analysed to determine whether local food availability is a good predictor of bird species composition and abundance. Whether birds on these islands separate food resources temporally could be examined from assessment of abundance and feeding patterns at different points throughout the day. A further option would be to compare the dialects of birds on different islands from sonogram analysis.

Extended Project Summary


MA136 Niche separation and the impacts of disturbance on bird communities in the dry forest

(18 June – 28 July)

This project has a waiting list

Birds are often used as indicator species for overall ecosystem condition, with species from different ecological niches being impacted to varying degrees by habitat disturbance. The avifauna of the Mahamavo forests contains a number of restricted range species, and other species being restricted to particular habitats. Students choosing this subject will undertake timed species counts and mist net surveys to make comparisons between bird communities in different habitat types and between differing levels of human habitat disturbance. Species distribution models using the spatial records for a given species can then be constructed and the percentage of the variability that can be explained by various environmental covariates (e.g. elevation, climate, land cover) determined in order to construct and validate a statistical model of the probability that a given species will be found in a particular landscape unit. These models can then be expressed as a habitat suitability map and the overlap between these species used to determine the level of niche separation. These dissertation subjects will contribute to our understanding of the avian communities of Mahamavo, and in particular to determining the habitat preferences and relative impacts of habitat disturbance on the bird species from different ecological niches and of different levels of conservation priority.

Extended Project Summary


ME141 Bird diversity and distribution in relation to forest structure in the Calakmul Biosphere Reserve, Mexico

(start dates 12 June or 26 June; need to have completed ME001)

The Calakmul Biosphere Reserve has extremely high bird diversity with over 360 resident bird species, many of which are endemic. Due to the traditional farming methods of the Ancient Mayans and their direct descendants living in the buffer zone of the reserve, Calakmul contains a large expanse of old growth forest in the core zone, and old growth forest and regenerating forests of various ages in the buffer zone. In addition, there is a notable rainfall gradient from the north to the south of the reserve that results in a gradual change in forest structure and tree species composition. Diversity of forest dwelling birds generally decreases with forest disturbance, but a study from one buffer zone community in Calakmul unexpectedly found that both bird abundance and diversity remained constant across regenerating forests of various ages and old growth forest. As the first Mayan settlers arrived in the Calakmul region before the forest appeared (the climate was too dry to support forest until relatively recently), it is possible that the bird population has evolved with the Mayan farming methods and thus the birds have adapted to using all forest types. The abundance and diversity of birds in Calakmul can be monitored using point counts and mist netting at multiple research locations in the reserve. These data will be collected across a range of transects in the reserve that encompass different habitat characteristics. Each transect contains a number of 20m x 20m habitat survey plots that provide detailed information of the forest characteristics in the area. In each of these plots, tree species will be identified, tree DBH, understorey vegetation, canopy openness, and the number of saplings will be measured. Bird data from each transect can then be related to mean habitat characteristics for the transect and comparisons between bird diversity and habitat variables may be investigated.

Extended Project Summary


PE156 Population structure and abundance of understorey birds

This project has a waiting list

The Pacaya-Samiria National Reserve is host to over 500 bird species, representing 64% of all the bird species found in Peru. More than 135 understorey bird species have been recorded within the reserve. On this project mist netting will be used to collect data on the tropical understorey bird assemblages within the reserve, offering valuable information on the lower and mid-storey birds not recorded by any other method. Mist nets are set for 5 days in each location and riverine habitat, open understorey flooded forests, levee forests and palm swamps are surveyed within the flooded forest. The number of repeats on each habitat type is largely influenced by the water levels experienced each year. A series of morphological measurements are recorded for each captured bird and birds are ringed before their release. The project could focus on a variety of topics and utilise the long term datasets. One project could identify the abundance of species found in different habitat types and their response to different water levels.

Extended Project Summary


TR167 Changes in bird communities in Tarnava Mare and habitat associations

(start date 28 June)

Point counts for 10 minutes of all birds seen or heard were completed twice at each of nearly 300 sites across the Tarnava Mare region in 2014, 2015 & 2016 and at nearly 200 of those same sites in 2013. The 300 sites are being resurveyed in 2017 and these datasets, together with those from previous years, would enable a number of different questions to be addressed. For example, what changes in the bird communities over the study period have been noted? What are the preferred habitats of the main species and how has the proportion of these habitats changed over the study period? If farming practices change how could this affect the bird communities? Are there species which could be used as indicators of habitat quality? This project is data rich and should enable some complex analyses to be performed.

Extended Project Summary