Luciano N. Segura

BOTFLY PARASITISM EFFECTS ON NESTLING GROWTH AND MORTALITY OF RED-CRESTED CARDINALS

Abstract We collected observational data in three consecutive breeding seasons to study interactions between the botfly Philornis seguyi and Red-crested Cardinals (Paroaria coronata) in a temperate zone near the southern limit of Philornis distribution. We analyzed: (1) seasonal trends in prevalence of parasitism, (2) influence of botfly parasitism on nestling growth rate and survival, and (3) the association between nest site vegetation at different scales (i.e., nest tree, vegetation surrounding the nest tree, and landscape) and probability of botfly parasitism. Prevalence of parasitism was 28% and was higher later in the breeding season. Botfly parasitism produced sub-lethal (lower growth rate of nestlings that survive) and lethal (lower nestling survival) effects. The lethal effect was negatively associated with age at the time nestlings were parasitized. Botfly parasitism was not associated with vegetation characteristics at the level of nesting tree or vegetation surrounding the nesting tree, but was associated with landscape features. Parasite prevalence was higher in large continuous woodland patches than in small isolated patches. However, we did not observe increased use of isolated patches of forest by Red-crested Cardinals, suggesting that use of nest sites with high botfly parasite intensity could be the consequence of high host density.

Microhabitat Nest Cover Effect on Nest Survival of the Red-Crested Cardinal

Abstract We evaluated the influence of microhabitat vegetation cover on Red-crested Cardinal (Paroaria coronata) nest survival in natural forests in central eastern Argentina by monitoring 106 nests for 1,262 exposure days. Daily nest survival rates increased with vegetation cover above the nest and decreased linearly as the breeding season progressed. Increased concealment above the nest helped hide and protect nests from predators (mainly aerial predators). Earlier nesting attempts in the breeding season were more successful than those later in the season. This is the first study to evaluate the effect of microhabitat vegetation cover on daily nest survival rates of a south temperate passerine. We highlight the importance of microhabitat nest concealment on nest success of the Red-crested Cardinal.

Red-crested Cardinals use color and width as cues to reject Shiny Cowbird eggs

ABSTRACT As part of the coevolutionary process between brood parasites and their hosts, the latter have developed different strategies to discriminate and reject parasitic eggs. This recognition–rejection process is the primary host defense against costly brood parasitism. The Red-crested Cardinal (Paroaria coronata) is an occasional host of the generalist Shiny Cowbird (Molothrus bonariensis) that successfully rejects all parasitic eggs. We studied the cues used by Red-crested Cardinals to recognize and reject foreign eggs by experimentally adding real parasite and host eggs painted as mimetic or nonmimetic of host eggs and analyzing whether eggshell coloration and/or shape were used as cues for egg rejection. Rejection rates, mostly through egg ejection, were high for all nonmimetic eggs (95% for unpainted cowbird eggs and 100% for painted nonmimetic cowbird and host eggs). On the contrary, they were low for mimetic host eggs (6% for unpainted host eggs and 20% for painted mimetic host eggs), but intermediate for painted mimetic cowbird eggs (55%). We also found that egg width significantly affected the probability of rejection, with wider parasitic eggs (i.e. more different from host eggs) more frequently rejected. We report for the first time that egg width is an important cue for recognition and ejection of cowbird eggs in an open-cup-nesting host. Our results show that coloration is a reliable cue used by Red-crested Cardinals to discriminate and reject parasitic eggs, but when coloration alone does not allow discrimination of foreign eggs, this host uses egg width as an additional cue.

Nest Survival and Predation in Blue-Fronted Parrots Amazona aestiva: Effects of Nesting Behaviour and Cavity Characteristics

In this study we analyse factors affecting nest survival in Blue-fronted Parrots Amazona aestiva breeding in the Chaco region of northern Argentina. We combined temporal and environmental variables in order to determine which best explain variation in overall nest survival and in predation dependent nest survival. We predicted that high and deep cavities, that are inaccessible to snakes and other predators, would have high daily survival rates. We compared the relative effects on nest survival of time of the breeding season, stage of the nesting cycle, and characteristics of the nest cavity. We modelled daily survival rate (DSR) for all observed nests, and daily survival rate for nests that had been predated (daily survival rate in relation to predation exclusively, DSRp). Nest predation accounted for 50% of nest failures. DSR was on average 0.989, translating into an apparent hatching success of 0.39. DSR decreased with time of breeding and increased with nest age. DSRp decreased with time of breeding and inclination of the nest cavity entrance hole and increased with height from the ground of the entrance hole. There was a quadratic effect of nest age on DSRp, such that daily survival was highest during incubation, lowest at hatching and the early nestling stage, but increasing throughout the remainder of the nestling stage. This effect became more pronounced as the breeding season advanced. Year and observer effects did not affect the probability of survival. Temporal patterns and characteristics of the nest cavity explained most of the variation in nest survival in Blue-fronted Parrots, which highlights the relevance of including these covariates in future studies of nest survival in parrots, and has important management and conservation implications.

Nesting biology of the Red-crested Cardinal (Paroaria coronata) in south temperate forests of central Argentina.

ABSTRACT Studies on breeding biology in Neotropical birds are crucial for understanding different aspects of their life histories and also for their conservation. We describe the nesting biology of the Red-crested Cardinal (Paroaria coronata) in central Argentina, a common suboscine that inhabits south temperate forests. We monitored 367 nests from October to February 2005–2008. Nest initiation followed a unimodal distribution with a peak in November. Within the forest, no nests were built on exotic tree species. Mean clutch size was 3.05 ± 0.05 eggs and decreased with time within the breeding season; egg size did not vary across the breeding season. Nesting cycles lasted, on average, 25.8 ± 0.1 days (nest construction: 6.1 ± 0.4 days; incubation period: 11.9 ± 0.1 days; nestling period: 13.8 ± 0.1 days). At least one young fledged in 26% of nests, 62% were depredated, and 11% were abandoned. Egg survival rate was 0.95 ± 0.02, hatching success rate was 0.84 ± 0.02, and nestling survival rate was 0.81 ± 0.03. Partial nestling losses were detected in 45% of the nests, of which 52% were because of brood reduction. Each breeding pair had on average 4.4 ± 0.2 nesting attempts over the breeding season. Our results support the prediction that small clutch sizes are associated with extensive breeding seasons and several nesting attempts within a season. Except for the short incubation period, all other breeding features reported in this study differ from those of most north temperate birds and are consistent with the life history traits of Neotropical birds.

Breeding phenology and nest survival of Cinereous (Circus cinereus) and Long-winged (C. buffoni) Harriers in the agricultural landscapes of north-east Patagonia, Argentina

ABSTRACT We present novel data on breeding ecology and nest survival of the Cinereous (Circus cinereus) and Long-winged (C. buffoni) Harriers in modified grasslands of southern Argentina and we evaluate variations in daily nest survival rates (DSR) in relation to temporal and habitat variables. We studied three mixed nesting colonies embedded in agricultural landscapes along a road. We found that DSR decreased linearly with time of breeding and increased with vegetation height above the nest and the distance to the road. This is the first and most complete reproductive study concerning two species of conservation concern, namely the Cinereous and Long-winged Harriers in Patagonia. Our study provides valuable and novel insights into the population dynamics of these little-known species.

Southernmost record of Yellow-headed Vulture, Cathartes burrovianus Cassin, 1845 (Cathartiformes, Cathartidae), in Buenos Aires province, Argentina

We report the southernmost record of Yellow-headed Vulture, Cathartes burrovianus, in Punta Piedras, north-eastern Buenos Aires province, Argentina. This record implies the presence of this species in a new habitat: the Pampas ecoregion. Considering this and other records in Argentina and Uruguay, the species distribution could be extending south from its known range.

Breeding Phenology and New Host List of the Black-Headed Duck (Heteronetta atricapilla) In Argentina

ABSTRACT The Black-headed Duck (Heteronetta atricapilla) is a unique interspecific brood parasite among birds where the host species provides parental care for incubation only. Despite this unique system, there are few studies on this species biology and the list of hosts remains incomplete. We present information about breeding phenology of the Black-headed Duck and an updated list of hosts obtained from a comprehensive review of egg collections deposited in the most important natural science museums of Argentina. We include five new hosts to the list: Great Grebe (Podiceps major), Maguari Stork (Ciconia maguari), White-cheeked Pintail (Anas bahamensis), South American Stilt (Himantopus mexicanus), and Long-winged Harrier (Circus buffoni). We found that solitary nesting host species were more likely to be parasitized earlier during the breeding season than colonial nesting species. The Black-headed Duck has an extended breeding season in central Argentina (Aug–Feb) as it is able to use a variety of hosts that breed in different times during the breeding season. With this contribution, the new list rises to 23 documented hosts of the Black-headed Duck belonging to eight different waterfowl orders.

Genetic structure reveals management units for the yellow cardinal ( Gubernatrix cristata ), endangered by habitat loss and illegal trapping

The yellow cardinal, Gubernatrix cristata, is an endangered passerine from southern South America. Populations are declining due to the loss of their natural habitat, which has caused a fragmented distribution, and the continuous extraction of individuals from the wild, mainly males, to sell them as cage birds. In this study, we assess the genetic variability of remaining yellow cardinal’s populations and determine whether these populations represent independent management units. We found that the degree of geographic isolation of the remaining populations parallels the genetic differentiation of these populations for both mitochondrial and nuclear markers, and supports the delimitation of four management units for the yellow cardinal (three in Argentina and one in Uruguay). Assignment tests showed that geographic genetic differentiation can be used to assign seized individuals from illegal pet trade to their original populations and thus manage their release.

First record of Crataegus monogyna Jacq. (Rosales: Rosaceae) in Buenos Aires province, Argentina

Crataegus monogyna Jacq. (Rosales: Rosaceae) is cited and collected for the first time for Buenos Aires province, Argentina. Its distribution is extended within Argentina and southern South America, since it was only known from Rio Negro and Neuquen provinces in southern Argentina until now.