Risk Of Egg Predation Research Articles

Effect of egg type on the estimation of nest predation in passerines

We compared predation rates of artificial nests baited with different egg types with the predation rates on nests of the Brown-and-yellow Marshbird (Pseudoleistes virescens), a Neotropical passerine common in the same area, in Argentina. We used deserted natural nests as experimental nests, baited with either Japanese Quail (Coturnix coturnix) or Shiny Cowbird (Molothrus bonariensis) eggs. Each experimental nest was baited with one natural and one paraffin-filled egg. Experimental nests baited with quail eggs suffered lower predation and egg losses than those baited with cowbird eggs. The main cause of egg loss and nest mortality in “cowbird nests” was pecking behavior of cowbirds. However, when we removed the effect of cowbirds, differences still held. In this area, the Shiny Cowbird is common and is the main cause of reduced breeding success of several host species. “Quail nests” had higher nest and egg survival than active Brown-and-yellow Marshbird nests. In contrast, “cowbird nests” and active Brown-and-yellow Marshbird nests had similar nest and egg survival. Experimental nests baited with natural passerine eggs such as those of Shiny Cowbirds seem to approximate the natural nest and egg predation risk for passerines in our study area.

Male Parental Care in Greater Rheas (Rhea Americana) in Argentina

AbstractGreater Rheas (Rhea americana) are precocial birds that show uniparental male care. We evaluated the extent of nest attention by males and estimated its effect on viability and survival of eggs. We assessed whether male absences during incubation were constrained to avoid embryos reaching lethal temperatures or to minimize risk of egg predation. We estimated (1) effect of nest attention on viability of eggs by comparing egg temperature in nests with and without male attention; and (2) effect of male care on egg predation, by comparing survival of eggs in nests with and without male care. Rhea males attended the eggs for 42 days, but effective incubation started 5–7 days after laying of the first egg. The proportion of time that males spent at the nest increased from 64% during egg laying (days 1–10) up to 97.5% during mid and late incubation (days 20–40). Male absences occurred at the warmest hours of the day and their lengths were positively correlated with the temperature of the environment. Male nest attention reduced the rate of egg losses and kept eggs above lower lethal temperatures for embryos during the night. We also estimated relative cost of parental care after hatching by comparing the time allocated to feeding and vigilance by males with chicks, males in nonreproductive groups, and nonreproductive solitary males. Males took care of the chicks for 4–6 months. They allocated less time to feeding and more time to vigilance than males in groups of adults or solitary males. Investment in vigilance decreased as chicks aged. Our results indicate that Greater Rhea males would require high levels of energetic reserves to start a breeding attempt. That high demand could explain why less than only 20% of the males attempt to nest during a breeding season.

MALE PARENTAL CARE IN GREATER RHEAS (RHEA AMERICANA) IN ARGENTINA

Abstract Greater Rheas (Rhea americana) are precocial birds that show uniparental male care. We evaluated the extent of nest attention by males and estimated its effect on viability and survival of eggs. We assessed whether male absences during incubation were constrained to avoid embryos reaching lethal temperatures or to minimize risk of egg predation. We estimated (1) effect of nest attention on viability of eggs by comparing egg temperature in nests with and without male attention; and (2) effect of male care on egg predation, by comparing survival of eggs in nests with and without male care. Rhea males attended the eggs for 42 days, but effective incubation started 5–7 days after laying of the first egg. The proportion of time that males spent at the nest increased from 64% during egg laying (days 1–10) up to 97.5% during mid and late incubation (days 20–40). Male absences occurred at the warmest hours of the day and their lengths were positively correlated with the temperature of the environment. Ma...

Oviposition patterns in a predatory mite reduce the risk of egg predation caused by prey

Abstract 1. Predatory arthropods lay their eggs such that their offspring have sufficient prey at their disposal and run a low risk of being eaten by conspecific and heterospecific predators, but what happens if the prey attacks eggs of the predator?2. The egg distribution and time allocation of adult female predatory mites Iphiseius degenerans as affected by predation of their eggs by prey, the western flower thrips Frankliniella occidentalis, were studied on sweet pepper plants. The predatory mites attack the first instar of thrips but all active stages of thrips are capable of killing the eggs of the predator; however the predatory mite is used for biological control of thrips.3. The majority of predatory mite eggs was laid on the underside of leaves in hair tufts (domatia). During the experiment, females spent increasing amounts of time in flowers where they fed on pollen and thrips larvae. The risk of predation on predator eggs by thrips was lower on leaves than in flowers where the majority of thrips resides. Moreover, predation risk was higher outside leaf domatia than inside.4. This suggests that predators avoid ovipositing in places with abundant prey to prevent their eggs from being eaten by thrips.

Conflict of interest between sexes over cooperation: a supergame on egg carrying and mating in a coreid bug

In the golden egg bug (Phyllomorpha laciniata Vill. Heteroptera: Coreidae) females lay eggs on the backs of conspecifics, often on courting males. Although the bugs do not provide care to the eggs, this decreases the risk of egg predation. As an effect males carry many eggs which are not their own. The male and female interests are in conflict; females need to find an oviposition site, and male fitness depends on the obtained number of matings. By using a very rare modeling approach, a supergame where the individuals actions change payoffs over time, we show that combinations of reciprocating strategies where males obtain a mating in return for a carried egg can be stable. The value of the mating, to males, is more important than the relatedness to the eggs in gaining their cooperation in carrying eggs. Females may also take advantage of the males without reciprocating. This is especially likely if the probability of future meeting is high and the value of a mating is high for the male. We relate our results to our own data from empirical studies and experiments on the species. In the light of the results we discuss the behavior of the bugs in relation to nuptial gifts. We also discuss the general applicability of the supergame approach.

Interactions between cleaning gobies and territorial damselfish on coral reefs

We studied the interactions between cleaning gobies,Elacatinusspp., at cleaning stations and territorial dusky damselfish,Stegastes fuscus, on a Barbadian fringing reef to enhance our understanding of the behavioural impact of cleaning stations on members of a coral reef community. Cleaning stations within damselfish territories were visited by significantly fewer species and fewer individuals than those outside damselfish territories. At cleaning stations within damselfish territories, the main client was the territory holder itself. Client behaviour did not differ between the two types of cleaning station; however, cleaning gobies at stations within damselfish territories spent less time cleaning clients, their cleaning bouts were shorter, and their feeding rate on clients was slower. These effects appear to be due to the repeated aggression of territorial damselfish towards fish intruding on to their territories to visit cleaning stations. The overlap between a territorial damselfish and a cleaning station therefore appears to have detrimental impacts on cleaning goby foraging. The presence of cleaning stations within damselfish territories exerted some effects on the territory owners. Although the rates of intrusions were similar on territories with and without cleaning stations, damselfish with cleaning stations tended to chase intruders more often, had a lower foraging rate, and were at higher risk of egg predation because of increased intrusions by egg predators. A potential benefit to territorial damselfish is regular access to a cleaning station; however, the magnitude of this benefit is unknown. This study reveals that damselfish, which are ubiquitous on coral reefs, can generate significant variation in levels of use of cleaning stations, which leads to new questions relating to the settlement behaviour of both cleaning gobies and damselfish.

A comparative study of territoriality in intertidal and subtidal blennioids (Teleostei, Blennioidei)

This paper presents a comparative analysis of territoriality in three intertidal (Lipophrys pholis, Coryphoblennius galerita, Salaria pavo) and two subtidal (Tripterygion delaisi, Parablennius pilicornis) blennioid fishes. Focal-animal observations of males guarding eggs showed that: (i) intertidal species had smaller territories that were less frequently patrolled; (ii) in subtidal species feeding was limited to the territory, while in intertidal fishes a substantial proportion of the feeding acts occurred outside the defended area; (iii) intertidal species spent less time out of the nest and showed a lower level of locomotory activity; (iv) subtidal species were subjected to a higher number of territorial intrusions with more species intruding their territory, some of them potential egg predators; (v) subtidal species performed several water column displays that played a significant role in courtship, while in intertidal fishes these displays are almost absent. Signalling without the presence of a female was almost absent in intertidal species. It is argued that intertidal fishes minimize the time spent out of the nest and the loss of contact with the substrate, features that may be of high survival value in conditions of strong turbulence. Although intertidal species have a reduced time available for feeding, this may be compensated by lower levels of locomotory activity, territorial defense and risk of egg predation.

An Experimental Study of Incubation Effort in High-Arctic Barnacle Geese

We examined the cost of reproduction in high-Arctic barnacle geese (Branta leucopsis Bechstein) by manipulating the length of the incubation period by ± 5 days. Unmanipulated clutches were used as controls. Nests with prolonged incubation suffered a higher egg loss to predators than control nests and nests with shortened incubation. Among females with prolonged incubation, body condition at hatching was significant lower than among females with shortened incubation. These, however, did not increase their feeding effort to compensate for mass loss. Increased levels of parental effort did not affect adult return rate or date of arrival to the breeding ground the following season. Accordingly, there is no evidence from this study that barnacle geese invest in young at the expense of their own survival or future fecundity. We propose that breeding females retain some reserves at the end of laying in order to (i) incubate more continuously, thus shortening the incubation period and minimizing the risk of egg predation, and/or (ii) have a buffer against weight loss due to increased energy expenditure during inclement weather.

Age of Clutches in Nests and the Within-Nest Spawning-Site Preferences of Three Damselfish Species (Pomacentridae)

In numerous fish species, males provide exclusive parental of the offspring, and females often use male or nest characteristics to discriminate among potential nests. Little attention, however, has focused on the possibility that once females have chosen a nest, they may also make choices regarding where in the nest to lay their eggs. In this paper, we describe within-nest clutch-laying patterns in three damselfish species, Stegastes partitus, S. leucostictus, and Hypsypops rubicundus. In all three species, females prefer to deposit clutches contiguous to early-stage clutches and noncontiguous to late-stage clutches, even when earlyand late-stage clutches are only a single day apart in age. This pattern holds true both in nests containing multiple clutches and in nests containing single clutches. Despite these within-nest spawning-site preferences of females, we were unable to detect an effect of clutch location on clutch survival in S. partitus. We examined several explanations for the female within-nest spawning site preferences. These were as follows: (1) the observed egg-laying patterns reduce the risk of egg predation through a dilution effect; (2) clutches of different ages have different metabolic requirements, and the observed egg-laying patterns reduce competition (e.g., for oxygen) between clutches; (3) the within-nest preferences are a consequence of a between-nest preference for early-stage clutches; and (4) the observed egg-laying patterns are a response to patterns of male parental (e.g., males may provide more to younger clutches). We conclude that this differential care hypothesis is the most likely explanation for the female within-nest spawning-site preferences.

The egg bundles of the monogenean Dionchus remorae and their attachment to the gills of the remora, Echeneis naucrates

Gills of three remoras, Echeneis naucrates L., from Heron Island, Queensland, Australia had few adults but many attached egg bundles of the monogenean, Dionchus remorae. Studies of fresh, and preserved and cleared, primary gill lamellae bearing egg bundles and investigations with scanning electron microscopy and serial wax sections reveal proliferated host epithelium surrounding and embedding part of a loop of egg-shell material to which eggs are tethered, but eggs in each bundle hang free of gill tissue. This hyperplasia appears to anchor egg bundles to the host's gills. However, hyperplasia will take time to develop and cannot play a part in tethering newly laid egg bundles. Possible advantages to the parasite by attaching eggs to the gills of its host include improved oxygenation of the eggs, and a reduced risk of egg predation. Egg attachment by D. remorae to their remora hosts seems well adapted to successful larval invasion offish which exhibit phoresy.

Polygyny in the River Sculpin, Cottus hangiongensis (Pisces: Cottidae), with Special Reference to Male Mating Success

The river sculpin, Cottus hangiongensis, which is a rock-nest spawner and spawns during the period from late April to early June, was polygynous in the three rivers where it was studied. In a river population, no significant correlation was recognized between the size of nest rocks and the male's mating success (number of females which mated with a male). On the other hand, a significant correlation was found between male size and male mating success. Under experimental conditions with tiles of the same size, larger males mated with a larger number of females. These observations suggest that male size is the most important determinant of female nest-choice and of male mating success. Females appear to minimize the risk of egg-predation by mating with those males which have a large body size and may thus have a greater advantage in driving away predators. The evolution of polygyny in this species may be explained by a model invoking female choice of male.