Nestling Loss Research Articles

An observation of parental infanticide in Dickcissels (Spiza americana): video evidence and potential mechanisms

ABSTRACT Brood reduction by parents via infanticide is considered rare in passerine birds; however, this behavior may be underreported because of the difficulties observing behaviors at the nest and because researchers tend to attribute partial nestling loss to other causes. Here, we report a confirmed incidence of parental infanticide by Dickcissels (Spiza americana). While video-recording parental behavior, we documented a 4-day-old nestling being removed by a female Dickcissel. This bird was also observed brooding and feeding, so this event was likely a parental infanticide. We subsequently examined monitoring data from 162 hatched Dickcissel nests across 2 breeding seasons to identify instances of unexplained partial nestling loss, which could potentially be attributable to infanticide. Our data indicate that 9.1–12.7% of hatched nests experienced these events. Infanticide by genetic parents could (1) benefit survival of remaining brood mates by reducing food requirements, disease, or predation risk; ...

Impact of Weather on Partial Loss of Nestlings in the Red-Backed ShrikeLanius collurioin Eastern Poland

Abstract. The influence of ambient temperature and rainfall on the size of partial losses in broods of the Red-backed Shrike was studied in the extensive agricultural landscape of eastern Poland in 1999–2003. Nestlings were divided into two age classes: up to the 5th day after hatching and the 6–10th day of life. The entire period of the nestlings' stay in the nest (1–10th day of life) was also considered. The ambient temperature did not influence the size of losses at either stage of the nestling life. Rainfall affected the size of nestling losses in the periods when they were 6–10 and 1–10 days old. The influence of rainfall explained only 11% of nestling losses. Thus, one should expect some factors other than weather conditions to cause partial losses in Red-backed Shrike broods in the study area, at least in seasons with an average pattern of air temperature and rainfall. Among such factors, the structure of territories variation in food abundance should undoubtedly be considered.

Effect of breeding timing on White-breasted Cormorant (Phalacrocorax carbo) reproductive success at a seasonally constant Kenyan lake

White-breasted Cormorant (Phalacrocorax carbo) breeding timing and reproductive success were documented in 1995 and 1996 at Lake Naivasha, Kenya (0°49'S), considered to be seasonally constant. In both years, pairs breeding earlier fledged significantly more chicks per breeding attempt than pairs breeding later. Smaller brood sizes later in the season were responsible for 81% of the difference; nestling loss represented 19%. Sixty-three percent of the total nestlings lost were from the nests of pairs breeding late in the season. Starvation appeared to be the primary cause of nestling loss, but there was no evidence of a consistent seasonal decline in prey availability. Neither predation nor sibling aggression appeared to be a major factor, although the reproductive success of late-breeders was almost certainly reduced by conspecific interference from fledglings of early-breeding pairs. The likeliest explanation for the seasonal decline is that older, more experienced (and therefore more successful) birds tend to breed early in the season.

Frequency of Egg and Nestling Destruction by Female Brown-headed Cowbirds at Grassland Nests

AbstractResearchers have suggested that Brown-headed Cowbirds (Molothrus ater) destroy nest contents of potential hosts to induce renesting and thus enhance future opportunities for parasitism. Although cowbird destruction of passerine nests has been witnessed and surmised, few data are available on frequency of those events. We used miniature video-cameras at nests of grassland passerines and documented partial or complete destruction of eggs or nestlings by cowbirds at 7 of 132 nests monitored with cameras. At least three of the seven cases appeared to be attempts to totally destroy the nest contents; those cowbirds did not appear to be motivated by food or an intent to parasitize the nest. Three cases probably were associated with parasitism, but two involved egg removal late in incubation and the third was unusually destructive. Cowbirds were responsible for 24% of egg losses and 5% of nestling losses caused by predators. The importance of cowbirds as an agent of egg and nestling loss undoubtedly varies among sites and years, but it should not be overlooked.

Frequency of Egg and Nestling Destruction by Female Brown-Headed Cowbirds at Grassland Nests

Researchers have suggested that Brown-headed Cowbirds (Molothrus ater) destroy nest contents of potential hosts to induce renesting and thus enhance future opportunities for parasitism. Although cowbird destruction of passerine nests has been witnessed and surmised, few data are available on frequency of those events. We used miniature video-cameras at nests of grassland passerines and documented partial or complete destruction of eggs or nestlings by cowbirds at 7 of 132 nests monitored with cameras. At least three of the seven cases appeared to be attempts to totally destroy the nest contents; those cowbirds did not appear to be motivated by food or an intent to parasitize the nest. Three cases probably were associated with parasitism, but two involved egg removal late in incubation and the third was unusually destructive. Cowbirds were responsible for 24% of egg losses and 5% of nestling losses caused by predators. The importance of cowbirds as an agent of egg and nestling loss undoubtedly varies among sites and years, but it should not be overlooked.

Frequency of Egg and Nestling Destruction by Female Brown-headed Cowbirds at Grassland Nests

Abstract Researchers have suggested that Brown-headed Cowbirds (Molothrus ater) destroy nest contents of potential hosts to induce renesting and thus enhance future opportunities for parasitism. Although cowbird destruction of passerine nests has been witnessed and surmised, few data are available on frequency of those events. We used miniature video-cameras at nests of grassland passerines and documented partial or complete destruction of eggs or nestlings by cowbirds at 7 of 132 nests monitored with cameras. At least three of the seven cases appeared to be attempts to totally destroy the nest contents; those cowbirds did not appear to be motivated by food or an intent to parasitize the nest. Three cases probably were associated with parasitism, but two involved egg removal late in incubation and the third was unusually destructive. Cowbirds were responsible for 24% of egg losses and 5% of nestling losses caused by predators. The importance of cowbirds as an agent of egg and nestling loss undoubtedly var...

Fitness Components Associated with Laying Date in the Cliff Swallow

We report how clutch size, annual reproductive success, and annual survival of breeders and offspring vary with laying date in Cliff Swallows (Petrochelidon pyrrhonota) in southwestern Nebraska, from 1982-1993. Clutch size declined significantly across the season for both parasite-free (fumigated) and naturally infested nests. Larger clutches of 4 and 5 eggs were initiated significantly earlier in warm and dry seasons; laying dates for smaller clutches showed no relationship with weather. Incubation period declined significantly with laying date and was shorter in the absence of ectoparasites. Fledging success declined significantly with laying date in nonfumigated nests, primarily through greater loss of nestlings to parasitic swallow bugs (Oeciacus vicarius). First-year survival probabilities of offspring varied significantly with date among nonfumigated nests but not among fumigated nests; earlier-hatched young survived best in some years, and in other years intermediate- or late-hatched young had highest survival. Number of young locally recruited was highest for early nesters in 5 of 7 years with intermediate nesters doing best in the remaining years. Annual survival of female breeders increased with laying date, suggesting a benefit to late nesting and a potential life history trade-off between reproduction and adult survival. Nestling body mass did not vary with laying date, suggesting no decline in food availability over the summer. Female body mass prior to and during laying declined significantly with laying date but during brood rearing increased significantly with laying date. Female body mass had no significant effect on clutch size independent of laying date. The primary environmental factor causing the seasonal decline in reproductive success is ectoparasitism. A seasonal decline in clutch size may be a strategic adjustment to reduce ectoparasitism by lowering the parasite carrying capacity per nest. Greater apparent survival of late-nesting females may prevent directional selection for earlier breeding times in Cliff Swallows.

Competition and coexistence of the European Bee‐eater Merops apiaster and the Blue‐cheeked Bee‐eater Merops persicus in Asia

Studies were conducted over a 10‐year period on the supposedly similar European Bee‐eater Merops apiaster and Blue‐cheeked Bee‐eater Merops persicus breeding in mixed and separate colonies in four Asiatic countries. In spring, M. persicus arrived a few days later and laid up to 2 weeks later than M. apiaster. Spatial distributions of the two species were positively associated. They were sympatric and syntopic: more than half of the local breeding ranges overlapped, and many birds bred within sight and sound of the congener. Intraspecific conflict was frequent, but in mixed colonies interspecific conflict was rare. Most M. apiaster nest burrows were dug into cliffs and most M. persicus ones into level ground, but dense mixed colonies occurred only in cliffs. Burrow architecture differed specifically. Diets were qualitatively similar at insect family level but different at the species level, partly because of local variation in availability and partly because of distinct preferences of M. apiaster for small beetles, ants and termites and of M. persicus for large dragonflies and cicadas. Merops persicus was less specialized than M. apiaster and had an airborne insect prey spectrum nearly twice as broad. Diets were more alike where the two birds foraged together than where they foraged separately. There was a high incidence of egg and nestling loss by predation and starvation.We speculate that each species may prove to breed more successfully in mixed than in monospecific colonies. We propose that the two bee‐eaters do not compete for nest sites but may compete for food and coexist unaggressively by trading off food competition against improved breeding success in mixed colonies.

Rufous-and-White Wrens Kill House Wren Nestlings during a Food Shortage

Birds of several species have been reported to kill immature birds of other species in contexts other than predation. Contexts include: (1) takeover of specialized nesting sites such as cavities (e.g., Kendeigh 1941, Pinkowski 1977), (2) brood parasitism (reviewed by Payne 1977), and (3) elimination of potential competitors for food (suggested by Picman 1977, 1980 for Long-billed Marsh Wrens [Cistothorus palustris]; Belles-Isles and Picman 1986 for temperate House Wrens [Troglodytes aedon]). The latter context is problematical because it cannot be inferred without evidence of actual or potential food limitation. In this note I document interspecific infanticide of tropical House Wrens by Rufousand-White Wrens (Thryothorus rufalbus). The infanticide appears to be based on competition for food since nestlings were killed only during an 8-week food shortage within a 4-year period. The infanticide was detected during a study of House Wrens conducted between 1982 and 1985 near the rural village of La Laguna, Republic of Panama (approximately 25 km northeast of Panama City). Six attacks occurred between 23 May and 14 July 1983; three were observed and three have been inferred (Table 1). On 23 and 24 May, a Rufous-and-White Wren was perched at the entrance of a nest box containing three House Wren nestlings (3 days old on 23 May). The box was mounted on a 1.25 cm diameter pole at a height of 1.6 m. The intruder thrust its head and beak rapidly and repeatedly into the nest and threw out one nestling on the first day. This nestling, as well as one of the remaining nestlings, had lacerations on the head and abdomen and puncture wounds on the abdomen. Thereafter one nestling was missing each day for two days. Parental House Wrens returning to the nest were driven away by the intruder during both days of observation. In a second case, on 9 July, an observer frightened a Rufous-and-White Wren from its perched position at the entrance of the nest box shortly after it commenced thrusting its head repeatedly inside the box. This nest contained six nestlings 10 days old. No mortality or injury resulted from this interrupted attack, and there was no evidence of repeated visits (i.e., no nestling loss or injury) for 3 days, after which a snake ate the nestlings. This second nest was located 3 km from the first, suggesting that two different Rufous-and-White Wrens were responsible for these incidents. In a third case, on 19 June, a Rufous-andWhite Wren repeatedly pecked a House Wren fledgling for 15 sec in a family group of recent fledglings and parents. The fledgling escaped and was observed 5 days later. This incident took place approximately 100 m from the first incident. The House Wren breeding season extended through October of 1983 (approximate length 24 weeks), but no further direct interactions between the two wrens were observed. Three additional nest losses (one partial) between late May and mid-July of 1983 may have been caused by Rufous-and-White Wrens because of similar patterns of lacerations and puncture wounds on the bodies of dead or dying nestlings (Table 1). One nestling had a severely broken tibiotarsus as well. Rufous-and-White Wrens were seen or heard within 25 m of these nests on the day of detection of infanticide. The nests were located at least 1 km apart and between 200 to 1,300 m from the nests mentioned above, suggesting that the Rufous-and-White Wrens seen in the vicinity of these nests were different individuals. Some alternative causes of the infanticide can be eliminated. Predators were probably not responsible for the killings because the dead or dying nestlings were not eaten. Infanticide by other House Wrens, associated with takeovers of mates or territories during each

Maguari Stork Nesting: Juvenile Growth and Behavior

Abstract Although it has a wide range in tropical South America, the Maguari Stork (Ciconia maguari) is poorly known. In an 11-yr study of its breeding biology in the llanos of Venezuela I found the mean clutch size for 3 yr to be 3.2 eggs. The young hatched asynchronously at 29-32 days and usually made their first flight at 60-72 days. Data on egg sizes, weights, and a probable dump egg are given. The weight and growth of two siblings, plumage succession, and nestling and fledgling behaviors are described. The fledging success of eggs from 55 nests, over 9 yr, was 61%. Loss of eggs (presumably from snake predation) was higher than nestling loss. Although the asynchronously hatched young in a clutch varied greatly in weight and continued this difference throughout nestling life, no case of brood reduction was found in 123 nests during the study. Nestlings were fed mainly frogs and tadpoles, fish, eels, and aquatic rats; food classes and food sizes brought by adults varied with the age of their young. Maguari Stork nestlings do not grasp with their hallux and so are confined to their nests until they can fly. I suggest that the two black plumages of nestlings, between the white hatching down and the white first basic plumage, are for crypsis of the nest-bound young.

The Breeding Biology of the Red-Vented BulbulPycnonotus Caferin Fiji

SUMMARYWATLING, Dick, 1983. The breeding biology of the Red-vented Bulbul Pycnonotus cafer in Fiji. Emu 83: 173–180.In Fiji, the Red-vented Bulbul Pycnonotus cafer has a distinct breeding season which occurs during the rains. The Bulbul has a mean clutch size of 2.5. There is a high rate of egg and nestling loss; 72% of eggs laid do not hatch and 53% of nestlings do not survive. Bulbuls have an extended period of parental care of fledglings and are unlikely to raise more than one brood in a season. Fledgling survival appears to be good and the annual recruitment rate is probably about 30%, although in one year it was considerably less.

On Behavior and Nesting of McConnell's Flycatcher (Pipromorpha macconnelli): Does Female Rejection Lead to Male Promiscuity?

Near Manaus, Brazil, McConnell's Flycatcher (Pipromorpha macconnelli), a small Amazonian tyrant-flycatcher very like the sympatric Ochre-bellied Flycatcher (P. oleaginea), tends to be a bird of forest and oleaginea a bird of second-growth. Calls of male macconnelli at singing areas near forest creeks are more like those of the southern Brazilian P. rufiventris than calls of oleaginea; in contrast to both, macconnelli displays close to the ground. Nests of macconnelli are oven-shaped and hang over forest creeks. Three small white eggs are laid on alternate days. Incubation and nestling periods are about 19 days each. Incubation and brooding constancy are low, and young grow very slowly. There is considerable brood reduction or loss of nestlings (one out of every three), although loss of nests is only 1.4% per day (45% loss in 43 days). One case of brood reduction was associated with rainy weather, but the species is nesting January-March, at the height of the rainy season. Possibly females care for nests alone because males would raise predation or lower uncertain food supplies near nests, especially in rainy or difficult periods. Promiscuity of males in this and other lek species may thus arise because of female rejection of male help, not because of male dominance of good sites as in polygamous species.