Parrot Nests Research Articles

Vines and canopy contact: a route for snake predation on parrot nests

Ornithologists have hypothesized that some tropical forest birds avoid snake predation by nesting in isolated trees that do not have vines and canopy contact with neighbouring trees. Here we review two complementary studies that support this hypothesis by demonstrating (1) that an abundance of vines and an interlocking canopy characterized Jamaican Black-billed Parrot Amazona agilis nest-trees that failed due to chick loss, presumably to snakes, and (2) that such trees were used preferentially by an arboreal snake congeneric to the snake implicated in the parrot losses. Evidence strongly suggested that losses of nestling Black-billed Parrots were due in substantial part to predation by the Jamaican (yellow) Boa Epicrates subflavus (Boidae). Studies of the closely related Epicrates inornatus on Puerto Rico revealed that trees used by boas had more vine cover and more crown or canopy contact with neighbouring trees than did randomly selected trees. Moreover, the boas had relatively large home ranges and were most active during March to July, which corresponds with the breeding season of parrots as well as other bird species. We suggest that nest failure due to snakes may be reduced in endangered bird species through isolating the nest-tree by eliminating vines and canopy contact with neighbouring trees and shrubs and by placing barriers on the nest-tree trunk.

Impact of protection on nest take and nesting success of parrots in Africa, Asia and Australasia

AbstractWild parrots represent one of the greatest commercial interests in the legal trade in wild birds. Although it is difficult to quantify, there is a considerable illegal trade in wild parrots. Thirty‐six per cent of the world's parrot species are listed by the International Union for the Conservation of Nature as threatened or near threatened, and 55% of these are threatened to some degree by trade. In this paper, we investigate the impact of protection on the number of nests that failed because of nestlings being taken by humans (hereafter nest take) and on nesting success in parrots. We collate data on parrot nest take from published and unpublished studies from Africa, Asia and Australasia, including countries and sites with and without national and local parrot protection measures in place. Nest take was insignificant in Australia, where all studies were from areas with both local and national protection. For less developed countries, levels of nest take were variable between studies, spanning the whole range from 0 to 100%. Protection significantly reduced nest take and correspondingly increased nesting success. Our results corroborate those for the Neotropics; thus, the advantages of protection appear to be independent of geographical location or political and economic conditions. We analysed data on legal trade in wild‐caught parrots before and after implementation of the 1992 Wild Bird Conservation Act (which practically eliminated import of parrots to the USA) and found that there was no apparent shift in parrot imports to other global regions from the Neotropics. We suggest that conservation of parrots globally would benefit from similar legislation introduced in other regions, such as the EU (15), which is responsible for more than 60% of global imports of wild parrots.

Climatic Variability, Nest Predation, and Reproductive Output of Lilac-Crowned Parrots (Amazona Finschi) in Tropical Dry Forest of Western Mexico

Abstract For 1996–2003, we determined reproductive output and success of 70 Lilaccrowned Parrot (Amazona finschi) nests in tropical dry forest of the Chamela-Cuixmala Biosphere Reserve in western Mexico. Only 42% of nests had young that fledged; predation was the main cause of nest failure. Low brood survival in 2000 and 2003 caused significant between-year variation in the probability of nest success during the nestling phase of the nest cycle. Reproductive output of Lilac-crowned Parrots was low, with females producing an average of 0.99 fledglings on an initial investment of 2.6 eggs. The fecundity component of clutch size varied significantly between years, because of the high median clutch size recorded in 2000. Nestling survival also varied significantly between years, creating large interannual fluctuations in reproductive output. The most productive breeding season was 1999, with an average output of 1.7 fledglings on an investment of 2.7 eggs; whereas the poorest breeding season was 2000, with an output of 0.57 fledglings from 3.3 eggs. Loss of reproductive potential was greatest in 2000 and 2003, because of brood reduction through starvation of later-hatched nestlings, with hatching order influencing the probability of nestling survival. Mean number of nestlings per egg-laying female was associated with interannual fluctuations in precipitation resulting from the El Niño-La Niña weather cycle in the Pacific Ocean. Both nest predation and food availability may limit parrot reproduction in tropical dry forests, with populations of threatened species in dry habitats being vulnerable to effects of climatic variability and habitat fragmentation.

The conservation implications of bird reproduction in the agricultural “matrix”: a case study of the vulnerable superb parrot of south-eastern Australia

Where agriculture has recently been imposed on natural systems, habitats that are modified, but not destroyed, within the agricultural matrix, are often, undervalued for their conservation benefits. Ecological research in the agricultural matrix in such landscapes has been limited in many countries. Yet many organisms live and breed in these landscapes. This paper outlines a large-scale case study of the vulnerable superb parrot that breeds in trees in the agricultural matrix of south-eastern Australia. Superb parrot nest trees were located, measured and compared with a set of randomly chosen non-nest trees. Increasing tree diameter had the largest influence over whether a superb parrot nested in a tree. There was a strong preference for nesting in dead trees and Blakely's red gum. There was limited eucalypt regeneration surrounding trees. The large size and poor health of nest trees requires urgent habitat management to provide alternative nest sites and regenerate trees across the whole agricultural matrix. This will require a long-term vision on the scale of centuries.

Present use and characteristics of Thick-billed Parrot nest sites in northwestern Mexico

Abstract Thick-billed Parrot (Rhynchopsitta pachyrhyncha) nest sites were studied during a six-year period (1995–2000) at six nesting areas in the Sierra Madre Occidental in Mexico. Nests were found in 187 snags or live trees of seven species, which averaged 75.2 cm dbh. Most nests were in snags (59%), and only two nests occurred in trees or snags under 40 cm dbh. Most nests occurred in Douglas fir (Pseudotsuga menziesii; 32.6%), and Mexican white pine (Pinus ayacahuite; 21.9%). Nest-site characteristics observed in the study were compared with those reported in the literature 20 yrs ago by Lanning and Shiflett (1983), and important differences were found in the percentages of tree species used. Decline of the Thick-billed Parrot seems to be related to large-scale logging over a wider historical breeding range. Commercial timber harvesting appears to affect nest site availability by leaving few snags and pine trees large enough for parrots to nest in.

CLIMATIC VARIABILITY, NEST PREDATION, AND REPRODUCTIVE OUTPUT OF LILAC-CROWNED PARROTS (AMAZONA FINSCHI) IN TROPICAL DRY FOREST OF WESTERN MEXICO

Abstract For 1996–2003, we determined reproductive output and success of 70 Lilaccrowned Parrot (Amazona finschi) nests in tropical dry forest of the Chamela-Cuixmala Biosphere Reserve in western Mexico. Only 42% of nests had young that fledged; predation was the main cause of nest failure. Low brood survival in 2000 and 2003 caused significant between-year variation in the probability of nest success during the nestling phase of the nest cycle. Reproductive output of Lilac-crowned Parrots was low, with females producing an average of 0.99 fledglings on an initial investment of 2.6 eggs. The fecundity component of clutch size varied significantly between years, because of the high median clutch size recorded in 2000. Nestling survival also varied significantly between years, creating large interannual fluctuations in reproductive output. The most productive breeding season was 1999, with an average output of 1.7 fledglings on an investment of 2.7 eggs; whereas the poorest breeding season was 2000, with an...

Overlap and competition for nest holes among eclectus parrots, palm cockatoos and sulphur-crested cockatoos

We examined the extent of overlap in the characteristics of nest holes used by eclectus parrots (Eclectus roratus), palm cockatoos (Probosciger aterrimus) and sulphur-crested cockatoos (Cacatua galerita) in patches of rainforest and woodland in and around Iron Range National Park, Cape York Peninsula, Australia. Eclectus parrots nested only in rainforest and palm cockatoos nested mostly in eucalypt woodland adjacent to rainforest. Sulphur-crested cockatoos nested in both habitats. Nest holes of eclectus parrots and rainforest sulphur-crested cockatoos were in trees of larger DBH (diameter at breast height) and higher off the ground than those of palm cockatoos and sulphur-crested cockatoos in woodland. Palm cockatoos differed from the other parrots in their use of deeper holes with entrances that faced skywards rather than sideways. Both palm cockatoos and woodland sulphur-crested cockatoos used nests with smaller entrances than eclectus parrots and rainforest sulphur-crested cockatoos. All species showed intraspecific competition for nest holes. Behavioural conflict was also common between sulphur-crested cockatoos and the other two species. Each year 9.7–25.8% of eclectus parrot nests were taken over either permanently or temporarily by sulphur-crested cockatoos. Only one palm cockatoo nest was taken over by sulphur-crested cockatoos. Nest-holes were destroyed by natural causes at similar rates in rainforest (3.8% per annum over 174 nest-years) and woodland (5.4% per annum over 93 nest-years). Four nest trees fell over, and the floor of the nest collapsed at a further four holes. Three woodland nest trees burnt down during dry-season fires (August–October). New eclectus parrot and rainforest sulphur-crested cockatoo holes originated from incipient hollows on the tree that were modified by the parrots. We discuss the intense competition between these large parrots in light of the apparent shortage of appropriate nest holes in Cape York rainforest and eucalypt woodland.

The breeding biology of Black-billed Parrot Amazona agilis and Yellow-billed Parrot Amazona collaria in Cockpit Country, Jamaica

Summary Black-billed Parrot Amazona agilis and Yellow-billed Parrot A. collaria are endemic to Jamaica and are restricted to remnant patches of mid-elevation wet limestone forest. Cockpit Country is the stronghold of Black-billed Parrot and is the only region where these two species occur sympatrically in significant numbers. In northern Cockpit Country, Black-billed Parrots nested commonly in degraded and regenerating edge habitat, where natural nesting cavities did not appear to be limiting. Yellow-billed Parrot nests were less abundant in the study area. Black-billed Parrots produced clutches of 3 or 4 eggs and incubation was approximately 24 days. Nestling growth and development were characteristically slow and the nestling period prolonged. Nesting success of both species was low for non-excavating, cavity-nesting species, but successful nests were prolific. Black-billed Parrot nestling mortality was highest during the first four weeks of the nestling period, the primary cause being predation, followed by ‘‘dead-in-nest, possible hypothermia’’. Many aspects of Black-billed and Yellow-billed Parrot nesting behaviour may be related to predation. The majority of predation events were attributed to the endemic and Vulnerable yellowboa Epicrates subflavus. Such predator–prey dynamics will challenge Jamaica’s natural resource managers to develop a more comprehensive attitude away from single-species conservation towards multiple species and their interactions in a complex habitat.

Natural ecotopes of Triatoma infestans dark morph and other sylvatic triatomines in the Bolivian Chaco

A survey of natural ecotopes of Triatoma infestans dark morph and other triatomine sylvatic species was performed in an uninhabited area of the Bolivian Chaco. Among the 321 triatomines collected by light trapping, only 4 T. infestans dark morph specimens were identified. Predominant flying species were T. guasayana and T. sordida group 2(51·7% and 37·1% of capture, respectively). The same species prevailed in terrestrial and epiphytic bromeliads where scarce T. infestans dark morph nymphal instars were also detected. In parrot nests T. delpontei prevailed broadly over other species (90·2% of the capture) and only 4 T. infestans dark morph adults were collected. In contrast, T. infestans dark morph was the predominant species captured in hollow trees (46·0% of the total collected). The abundance of immature forms (88·2% of the collection) shows that hollow trees constitute a favourable ecotope for this species. Of the 421 trees investigated, 33·7% were positive for triatomines. T. infestans dark morph, found inside 15·0% of them, also had higher apparent density than other species (average number of T. infestans in positive trees, 2·0 ± 1·6 vs 1·3 ± 0·6 for other species). Light trapping seems to be an efficient method to sample the T. sordida-T. guasayana complex in that it shows a similar distribution to that observed in natural ecotopes; however, this method is ineffective for the assessment of the local abundance of T. infestans dark morph.

Trade in the gray parrot Psittacus erithacus on the island of Principe (São Tomé and Principe, Central Africa): Initial assessment of the activity and its impact

The trade in Príncipe's gray parrot Psittacus erithacus population was assessed during a two-month stay on the island. It was established that the gray parrot nests throughout the island, including on cocoa plantations. Despite increasing commerce, it can still be considered a common species on the island. Techniques of capture, which yield a total of approximately 1500 chicks per year, in addition to an unspecified number of adults, are described. Since trade in the gray parrot is probably resulting in the depletion of the species, the assessment of the insular population and the evaluation of the impact of the activity are urgently needed. These studies should involve local hunters.