Incubation Behavior Research Articles

Food conditions affect yolk testosterone deposition but not incubation attendance

In many bird species with hatching asynchrony, yolk androgens increase across the laying sequence. This has been hypothesized to represent a compensatory mechanism for disadvantages of later-hatching chicks – via positive effects of yolk androgens on early competitiveness and growth. However, the costs and benefits of this compensatory strategy probably depend on environmental factors determining the survival chances of the chicks such as the food conditions, which should, therefore, influence maternal yolk androgen deposition.We studied the consequences of manipulated food conditions on the expected level of hatching asynchrony in canaries (Serinus canaria) assigning females to either a low (=LQ) or high quality (=HQ) diet. We measured the incubation behaviour (as incubation attendance) and the yolk androgen deposition in order to investigate whether and how females modulate hatching asynchrony in relation to the food conditions.Females on a HQ diet laid larger and heavier clutches, showed a stronger increase in yolk testosterone content towards the last-laid eggs, but did not alter their incubation attendance. Thus, females on a HQ diet seem to favour the survival of later hatching chicks, as indicated by their yolk testosterone deposition pattern. However, females on a HQ diet laid larger clutches and might need to compensate more in order to achieve a similar degree of hatching asynchrony than females on a LQ diet, given the lack of plasticity in incubation attendance. This suggests that canary females respond to food manipulations mainly via changes in clutch size rather than by altering the degree of hatching asynchrony.

State-dependent incubation behaviour in the high arctic barnacle geese

Energetic trade-offs between time spent on incubation and times spent on foraging for nesting birds give individuals in good body condition the possibility to incubate more continuously. In the present paper, the incubation behaviour of female barnacle geese Branta leucopsis was quantified in a colony in Svalbard. Females were weighted in early incubation and feeding recess lengths and frequencies were recorded. The feeding behaviour during the course of incubation was significantly correlated to by body mass, and heavy females had both fewer and shorter feeding recesses than lighter females. Moreover, there was an increase in the number of feeding recesses and the total feeding time as the incubation period progressed. Neither clutch size nor egg laying date had an effect on incubation behaviour. However, clutch size was positively related to female body mass suggesting that high-quality females produce large clutches but also allocate more body reserves to incubation. Females left the nest to feed at all times of the day, but more frequently during day time. This was not related to their body mass. Females presumably leave their nest at the time of day when the costs to reheat eggs are at a minimum. The diurnal rhythm may also be adjusted to the activity by egg predators. Overall the results support the state-dependent hypothesis for incubation behaviour, suggesting that body condition at the start of incubation is an important factor for incubation behaviour in barnacle geese.

WATER VAPOR CONDUCTANCE OF THE LOWER CRETACEOUS DINOSAURIAN EGGS FROM SANAGASTA, LA RIOJA, ARGENTINA: PALEOBIOLOGICAL AND PALEOECOLOGICAL IMPLICATIONS FOR SOUTH AMERICAN FAVEOLOOLITHID AND MEGALOOLITHID EGGS

The water vapor conductance (GH2O) of the neosauropod eggs from the Lower Cretaceous Sanagasta nesting site in La Rioja Province, Argentina, was examined and compared with other Cretaceous Argentinean oological material. The 2900 mgH2O/day·Torr GH2O of the Sanagasta eggshells confirms an extremely moist nesting environment and supports field observations of dug-out nests in a geothermal setting. The observed thinning of the outer eggshell surface during incubation increases gas conductance and concomitantly decreases eggshell mechanical resistance during the late ontogenetic stages, thus facilitating embryonic development and hatching. The Sanagasta and Entre Rios Province faveoloolithid eggs display the highest and comparable GH2O values and share several morphological and diagenetic characters, indicating comparable nesting strategy in geothermal settings. However, the faveoloolithid Yaminue and La Pampa Province specimens cluster together with lower GH2O values closer to the megaloolithid eggs. The GH2O of the megaloolithid egg Megaloolithus patagonicus was reconsidered and new results are now congruent with other reported megaloolithid GH2O values. Additionally, we hypothesize that Y-shaped pore canals of M. patagonicus, which upper sections reach only the top third or half eggshell thickness and, a wider section in the middle would not compromise the overall egg mechanical resistance like vertical pores connecting directly the outer to the inner eggshell surfaces. Such pore spatial arrangement and geometry would enhance, as the eggshell thins during incubation, a greater GH2O, GO2 and GCO2 and facilitate embryonic development in high moisture nesting contents. Overall, data suggests that neosauropod nesting and brooding behaviors were dependent on elevated moisture nesting environments.

Effects of egg oiling on ground-nesting double-crested cormorants at a colony in Lake Ontario: an examination of nest-attendance behaviour

Context We assessed the effects of egg oiling on ground-nesting double-crested cormorants (Phalacrocorax auritus) in the context of an emerging management strategy for the largest known cormorant colony on the lower Great Lakes. We designed the present study to answer specific questions in response to concerns raised by stakeholders and members of the public regarding this management technique. Aims The aim of the present study was to examine the behavioural response of adult cormorants to egg oiling. Prior work on this issue has focussed on population-response questions rather than the behavioural level. Consequently, detailed observations on how cormorants respond to egg oiling are lacking. Methods Using instantaneous and focal observations to measure behaviours, we compared Treatment nests (n = 24, 23) to Control (n = 24) and Sham (handled, but not treated; n = 24) nests. We observed nest attendance, incubation and mate-presence behaviour, and divided observations into pre-chick and entire-season categories for analysis. Key results Our study determined that egg oiling does not cause immediate nest desertion by adult birds; Treatment birds incubated their nests as long as did Sham and Control birds. We found no difference among the three groups in the proportion of time a mate was present during incubation for Control and Sham nests in the pre-chick period. We found that the total seasonal duration of nest attendance by Treatment birds was shorter than that for the birds in the other groups. Conclusions Both incubation and mate-presence data suggest that egg oiling did not measurably affect the behaviour of adult cormorants in the pre-chick period. Our study also suggests that Treatment birds attended their nest long enough to preclude re-nesting within the breeding season, although this may not apply for regions with longer nesting seasons. Implications Our study indicates that egg oiling, administered judiciously, may be an appropriate management technique for ground-nesting cormorants, although management targets must be clearly articulated.

Declining extra-pair paternity with laying order associated with initial incubation behavior, but independent of final clutch size in the blue tit

Although functional explanations for female engagement in extra-pair copulation have been studied extensively in birds, little is known about how extra-pair paternity is linked to other fundamental aspects of avian reproduction. However, recent studies indicate that the occurrence of extra-pair offspring may generally decline with laying order, possibly because stimulation by eggs induces incubation, which may suppress female motivation to acquire extra-pair paternity. Here we tested whether experimental inhibition of incubation during the laying phase, induced by the temporary removal of eggs, resulted in increased extra-pair paternity, in concert with a later cessation of laying, in blue tits (Cyanistes caeruleus). As expected, experimental females showed a more gradual increase in nocturnal incubation duration over the laying phase and produced larger clutches than controls. Moreover, incubation duration on the night after the first egg was laid predicted how extra-pair paternity declined with laying order, with less incubation being associated with more extra-pair offspring among the earliest eggs in the clutch. However, incubation duration on this first night was unrelated to our experimental treatment and independent of final clutch size. Consequently, the observed decline in extra-pair paternity with laying order was unaffected by our manipulation and larger clutches included proportionally fewer extra-pair offspring. We suggest that female physiological state prior to laying, associated with incubation at the onset of laying, determines motivation to acquire extra-pair paternity independent of final clutch size. This decline in proportion of extra-pair offspring with clutch size may be a general pattern within bird species.

Male incubation feeding in songbirds responds differently to nest predation risk across hemispheres

Evolution of parental care behaviour has been of considerable interest to behavioural ecologists for a long time. Incubation feeding, where an individual incubating eggs is provisioned by another individual, is an important component of avian parental care. It may be critical for breeding success by allowing the incubating bird to spend more time on the eggs. However, very little is known about environmental factors shaping incubation feeding, and incubation behaviour in general, of tropical and southern hemisphere birds, and how this differs compared to northern hemisphere species. We collated available data on the rate of incubation feeding in Australian, New Zealand and North American songbirds (78 species from 25 families). There was a strong positive relationship between female incubation attentiveness and incubation feeding by males; however, female attentiveness was higher in North America than in Australia and New Zealand for the same intensity of male incubation feeding. Incubation feeding was not related to species body mass, social organization, geographical latitude or ambient temperature. It differed significantly between families, but overall was not different between regions. Incubation feeding rate was related to nest predation rate, but differently in the two regions. It increased with nest predation rate in Australia and New Zealand, but decreased with nest predation rate in North America. We suggest that this may be caused by different predator–prey interactions in North America versus Australia and New Zealand, which could have shaped the evolution of incubation feeding differently. ► We model rates of male incubation feeding in songbirds across two continents. ► We use data obtained by a comprehensive review of published literature. ► Incubation feeding decreased with nest predation in North America. ► Incubation feeding increased with nest predation in Australia and New Zealand. ► Nest attentiveness increased with incubation feeding in both continents.

Seasonal patterns of prolactin and corticosterone secretion in an Antarctic seabird that moults during reproduction

In avian species that have evolved life-history strategies wherein molt and breeding overlap, there are potential conflicts between the regulatory roles of baseline prolactin and corticosterone in parental care (positive) and moult (negative). We describe seasonal patterns of hormonal secretion, moult, and parental behaviour in sibling species of giant petrels ( Macronectes spp.) which begin moult during the incubation/early chick-rearing stage of reproduction. With the exception of male Southern giant petrels ( Macronectes giganteus), prolactin secretion and moult in Northern ( Macronectes halli) and female Southern giant petrels conformed to those observed in all other avian species, with the initiation of moult coincident with decreases from peak prolactin levels. However, male Southern giant petrels began moulting early in incubation when prolactin was increasing and had not yet peaked, which suggests a requirement of prolactin for incubation behaviour and a dissociation of prolactin from moult. Corticosterone showed little seasonal variation and no relationship with moult. When comparing prolactin, corticosterone, and moult in failed vs. active breeders, we found that failed breeding enabled a more rapid down-regulation of prolactin, thus facilitating a more rapid moult. We present specific examples of the behavioural ecology of giant petrels which we conclude help mediate any potential hormonal conflicts between parental care and moult.

Review: an embryo's eye view of avian eggshell pigmentation

Current research into the evolution and adaptive function of avian eggshell pigmentation, including maculation, has focused mostly on signalling-based and structural function hypotheses but ignored the potential consequences of shell pigmentation for the developing avian embryo, especially in moderating the embryo's interaction with its light environment. The exposure of the eggs to sunlight that frequently accompanies avian incubation behaviour is one of the major evolutionary steps setting apart birds and reptiles, and coincides with the appearance of eggshell pigmentation. This suggests that shell pigments could play a major role in ensuring the successful development of the avian embryo. We propose that the effects of shell pigments on the egg contents should be considered in addition to established hypotheses of shell pigmentation such as crypsis, egg recognition or a possible structural function. This approach has the potential to identify trade-offs between different pigment functions and to resolve some of the long standing paradoxa in the evolution of eggshell colour, such as the occurrence of conspicuous blue eggs in passerines or the secondary evolution of white eggshells in cavity nesters. In particular, we identify seven hypotheses, which address how the interaction of eggshell pigments and the light environment may influence embryonic development. These hypotheses are the: thermo-regulation; UV-B protection; photo-acceleration; lateralization; circadian rhythm; photo-reactivation; and antimicrobial defence. We believe that the understanding of eggshell pigmentation will greatly benefit from taking these hypotheses into consideration when studying the functional significance of eggshell pigmentation and suggest a number of promising directions for future experimental and comparative research.

Incubation temperature affects multiple measures of immunocompetence in young wood ducks (Aix Sponsa)

Parental effects play a vital role in shaping offspring phenotype. In birds, incubation behaviour is a critical parental effect because it influences the early developmental environment and can therefore have lifelong consequences for offspring phenotype. Recent studies that manipulated incubation temperature found effects on hatchling body composition, condition and growth, suggesting that incubation temperature could also affect energetically costly physiological processes of young birds that are important to survival (e.g. immune responses). We artificially incubated wood duck (Aix sponsa) eggs at three biologically relevant temperatures. Following incubation, we used two immunoassays to measure acquired immune responses of ducklings. Ducklings incubated at the lowest temperature had reduced growth, body condition and responses to both of our immune challenges, compared with those from the higher temperatures. Our results show that incubation temperatures can be an important driver of phenotypic variation in avian populations.

Brooding and development of Anasterias minuta (Asteroidea: Forcipulata) in Patagonia, Argentina

Brooding, embryonic and larval development, and the influence of environmental and biological factors in tidepool habitats were studied in the sea star, Anasterias minuta, at various sites along ~220 km of the Patagonian coast. This species has a benthic, lecithotrophic development that includes eight distinct developmental stages. A larval organ, the connection cord, is developed from a small preoral lobe at early stages of development and becomes larger and thinner at advanced stages. Fecundity and average egg size increased with female body size. The regression of log egg number to log sea-star size and weight at different sites had a slope significantly less than 3.0, resulting in negative allometry and indicating that brood capacity was limited in large females. Development was generally synchronous among sites, but varied within each brood at advanced stages, with more developed brooded larvae located at the periphery of the brood mass. Brooding was synchronous among various populations at different years and spatial scales, and extended over a period of 8 months. The highest proportion of brooding females occurred during May and June (austral winter). Juveniles were released mainly during September. The likelihood of finding brooding sea stars decreased with increasing sea water temperature, tidal height, and wave exposure, and increased with increasing body size. Both body size of brooding females and brooding rate were higher in the infralittoral fringe than at midlittoral levels. A revision of the current model of brooding behavior and development among forcipulate sea stars is given.

Evolution of eggshell structure during rapid range expansion in a passerine bird

Summary1. Environmental factors such as temperature, humidity and partial oxygen pressure can affect avian eggshell structure because gas exchange across the shell must allow sufficient water loss while preventing dehydration of the embryo. Studies of species with known chronology of colonization of novel environments provide a powerful insight into the relative importance of ecological factors shaping the evolution of eggshell structure.2. Here, we examined changes in eggshell structure that accompanied rapid range expansion of house finches (Carpodacus mexicanus) across North America. We analysed thickness and pore density in eggshells from three ecologically distinct populations: the native desert population in southwestern Arizona and two 30‐year‐old populations in the northwestern (north‐west Montana) and southeastern (south‐east Alabama) parts of the species’ range. We also conducted cross‐foster exchanges of freshly laid eggs within and between the northwestern and southeastern populations to examine consequences of population differences in eggshell structure on embryo development.3. Eggshell structure was most distinct in a recently established population inhabiting higher humidity environment (southeastern Alabama), where eggs were the largest, eggshells the thickest and pore density the lowest. Populations that experienced highly distinct ambient temperatures (southwestern Arizona and northwestern Montana) nevertheless had similar eggshell structure. These results were corroborated by experiments where humidity differences between cross‐fostered nests had twice the effect on embryo survival compared to the effect of change in ambient temperature. Correspondingly, experimental egg exchanges between southeastern. Alabama and northwestern Montana populations were associated with fourfold increase in embryo mortality compared to within‐population egg exchanges.4. We document rapid evolution of eggshell structure in response to colonization of novel environments and establish the relative importance of environmental factors on avian eggshells. We discuss these results in relation to population variation in incubation behaviour and its ability to shield eggshell structure from the selection exerted by novel environments.

Combining field and aviary approaches to monitor incubation in ducks: importance of clutch size, body mass and weather

Capsule Clutch size and female body mass play major roles in duck incubation behaviour. Aims To investigate the effects of incubation stage, clutch size, body size, body mass and weather on incubation attentiveness. Methods Incubation behaviour was monitored with Temperature Data Loggers (TDLs). Nest temperature fluctuations were recorded both in the field in Common Pochards Aythya ferina and in aviaries in Mallards Anas platyrhynchos using TDLs deposited either in the nest (Pochards) or in a dummy egg placed in the clutch (Mallards). Both methods allowed data collection on incubation attentiveness. Results Incubation attentiveness increased over the incubation period and with clutch size for both species. Body size appeared to affect incubation rhythms in Mallards only. Female Pochards were found to reload their nest with fresh material in response to precipitation events, presumably owing to the rise in water level. Conclusions Clutch size and female body mass play major roles in duck incubation behaviour. Climatic events can also be prominent factors influencing incubation behaviour. We describe for the first time the nesting behaviour of Pochard females and show that they have the capacity to adjust nest topology in response to a rise in water level following rain.

Partial Incubation in Birds: Its Occurrence, Function, and Quantification

Early studies of incubation behavior acknowledged the existence of a less regular form of incubation that can occur from the beginning of egg laying to shortly after clutch completion. It has been variously termed “partial incubation” (Putnam , Seel , Ashkenazie and Safriel ), “brooding” (Barth ), “intermittent incubation” (Samuel ), “irregular incubation” (Beer ), or “nonrhythmic incubation” (Morton et al. ). This form of incubation has been described from visual observations of adults sitting on the nest less regularly, and from egg temperatures that are lower and more variable than those typically attained after clutch completion (Barth , Brackbill , Kendeigh , Barrett , Morton and Pereyra ). We refer to this little-understood behavior as “partial incubation” because it is characterized by a reduced amount of time during egg laying that parents sit on and warm their eggs, compared with the amount and intensity of incubation they provide later in the nesting cycle after the clutch is complete. Partial incubation is a common way for birds to initiate incubation. The onset of incubation, the moment at which a bird begins to incubate a clutch, is a critical event in the avian nesting cycle because it has important effects on fitness, as noted more than half a century ago by David Lack (). Incubation onset can affect hatching success and hatching patterns (Nilsson and Svensson , Wang and Beissinger ), nestling growth and development (Slagsvold et al. , Bitton et al. ), fledging success (Hebert , Hebert and McNeil ), and postfledging survival and recruitment (Cam et al. ). Not only can the onset of incubation affect adult reproductive rates, but it also influences and is influenced by parental body condition and survival (Hanssen et al. ). Yet the onset of incubation is rarely described and even less commonly quantified, and methods of determining incubation onset have not been standardized among studies or species. In this review, we () clarify terminology for the onset of incubation, refine the concept of partial incubation, and summarize the prevalence of partial incubation. We then () examine the potential functions of partial incubation, () map individual-level patterns of partial incubation from previous studies onto a recently developed typology of patterns for the onset of incubation (Wang and Beissinger ), and examine intraspecific variability and compare interspecific data with respect to taxonomic and ecological diversity. We also () provide a standardized method for determining the individual onset of full incubation, using complete records of nest attendance or incubation from the start of laying to beyond clutch completion. Our goal is to show how data from disparate studies can be used to test hypotheses about the function of partial incubation. Finally, we () offer questions that may prove to be fertile areas of research and suggest ways to standardize future data collection and analysis to benefit common research goals. TERMINOLOGY FOR THE ONSET OF INCUBATION

Dopamine and mesotocin neurotransmission during the transition from incubation to brooding in the turkey

We investigated the neuroendocrine changes involved in the transition from incubating eggs to brooding of the young in turkeys. Numbers of mesotocin (MT; the avian analog of mammalian oxytocin) immunoreactive (ir) neurons were higher in the nucleus paraventricularis magnocellularis (PVN) and nucleus supraopticus, pars ventralis (SOv) of late stage incubating hens compared to the layers. When incubating and laying hens were presented with poults, all incubating hens displayed brooding behavior. c-fos mRNA expression was found in several brain areas in brooding hens. The majority of c-fos mRNA expression by MT-ir neurons was observed in the PVN and SOv while the majority of c-fos mRNA expression in dopaminergic (DAergic) neurons was observed in the ventral part of the nucleus preopticus medialis (POM). Following intracerebroventricular injection of DA or oxytocin (OT) receptor antagonists, hens incubating eggs were introduced to poults. Over 80% of those injected with vehicle or the D1 DA receptor antagonist brooded poults, while over 80% of those receiving the D2 DA receptor antagonist or the OT receptor antagonist failed to brood the poults. The D2 DA/OT antagonist groups also displayed less c-fos mRNA in the dorsal part of POM and the medial part of the bed nucleus of the stria terminalis (BSTM) areas than did the D1 DA/vehicle groups. These data indicate that numerous brain areas are activated when incubating hens initially transition to poult brooding behavior. They also indicate that DAergic, through its D2 receptor, and MTergic systems may play a role in regulating brooding behaviors in birds.

Lattice-Mediated Propagation of Photoinduced Phase Transition in Co–Fe Cyanide

Spin-crossover compounds show many photoinduced phase transition (PIPT) phenomena, reflecting the strong coupling between the electron, spin, and lattice degrees of freedoms. In these compounds, the photoinduced electronic excitation triggers the intersystem of crossing in Fe2þ or Co3þ with a high probability, and alters the spin state of the transition metals (light-induced excited spin state trapping: LIESST). The spin state transition further causes local lattice deformation as a result of the variation in the ionic radii of Fe2þ or Co3þ.14) The resultant local lattice distortion modifies the electronic structure of the surrounding sites, causing a nonlinear response of the system. Ogawa et al. reported the threshold and incubation behaviors in the photoinduced phase transition of [Fe(2-pic)3]Cl2 EtOH (2-pic = 2-aminomethyl-pyridine) at 2.2K. Liu et al. reported a dynamical phase transition in Nafion–[Fe(Htrz)3] (Htrz = 1,2,4-4H-triazole) and an optical hysteresis in [Fe(pyz)6](BF4)2 (ptz = 1-propyltetrazole) at 77K. Several researchers theoretically investigated the photoinduced dynamics beyond the mean-field approximation, even though the approach had been successful in several situations. In this Note, we reported the mesoscale lattice effect on PIPT of a Co–Fe cyanide, Na0:27Co[Fe(CN)6]0:713.8H2O, at 200K by a microscopic spectroscopy. The compound shows a spin-crossover-type PIPT from the low-spin (LS) phase with LS Co3þ and LS Fe2þ to the high-spin (HS) phase with HS Co2þ and LS Fe3þ, accompanying a significant lattice expansion of 3%. We carefully investigated the PIPT dynamics at each position around the photoexcitation spot, which is 75 m in diameter. We found that the PIPT at each position takes place simultaneously within 0.2 s, even though the density (nHS) of the HS sites is widely distributed in the range of 0–0.6. The distribution of the linear expansion coefficient ( L=L) within the HS region suggests that the propagation of the PIPT region is mediated by a coherent lattice expansion. A thin film of Na0:27Co[Fe(CN)6]0:713.8H2O, 1310 nm in thickness, was electrochemically synthesized on an indium–tin oxide (ITO) transparent electrode. The chemical composition was determined by inductively coupled plasma (ICP) and CHN organic elementary analyses. The Xray diffraction pattern revealed that the compound is facecentered cubic with a lattice constant of a 1⁄4 10:34 A. The surface and cross-sectional scanning electron microscopy (SEM) images revealed that the film consists of rodlike crystals, 600 nm in length and 130 nm in area. The film shows a thermally induced LS–HS phase transition at 230K (1⁄4 Tc) in the warming run, and the film changes from violet (LS phase) to red (HS phase). The photoinduced dynamics was recorded with a laboratory-built microscopy system equipped with a charge-coupled device (CCD) camera. We used the second harmonics (532 nm) of the yttrium aluminum garnet (YAG) laser as the excitation light source. The spot size of the excitation light was 75 m, and the excitation density was 6.6 photon s 1 site . A notch filter was inserted to eliminate the scattering from the excitation light. The magnitudes of nHS at each time and position were determined by the chromaticity in the microscopy moving image. The spatial resolution of the system was 5 m. To increase the signal-to-noise ratio, the chromaticity was averaged within the 10 10 pixels around each position. Figure 1 shows examples of the microscopy images of the Na0:27Co[Fe(CN)6]0:713.8H2O film under photoirradiation at 200K at various times. The bright region corresponds to the HS region. No macroscopic PIPT is observed at (b) 41.7 s. The PIPT starts around the central region of the excitation spot at (c) 43.3 s, and then expands outside at (d) 43.5 s. A similar incubation behavior of the PIPT was observed in [Fe(2-pic)3]Cl2 EtOH. One may notice that the PIPT region at (d) 43.5 s extends beyond the excitation spot [broken-line circle in Fig. 1(a)]. The inset of Fig. 2(b) shows a prototypical example of the time dependence of nHS. (a) 0 .0 s

Prolactin plays a stimulatory role in ovarian follicular development and egg laying in chicken hens

The aim of this study was to show a stimulatory role in ovarian follicle development by prolactin (PRL) in chicken hens. In experiment 1, anti-PRL antibodies were generated in hen plasma by intramuscular administrations of recombinant PRL antigen. Egg laying remained at levels lower ( P < 0.05) in the PRL-immunized group than in the BSA-immunized group of hens, whereas development of incubation was depressed in the former but not the latter group. Throughout the experiment, plasma PRL concentrations were lower in the PRL-immunized hens than in non-incubating control hens; LH concentrations were similar between the PRL- and BSA-immunized hens until the end of the experiment when LH was lower in the BSA-immunized hens ( P < 0.05). In experiment 2, anti-PRL receptor (PRLR) antibodies were raised in hens with the use of immunizations against recombinant PRLR extracellular domain. Immunization against PRLR initially increased the egg-laying rate when measured under the short photoperiod (12 h) but blocked the laying rate increase that occurred in the BSA-immunized control hens when the photoperiod was extended from 12 to 16 h. The development of incubation behavior was not affected by immunization against PRLR nor was plasma PRL or LH concentration. In experiment 3, when the egg-laying rate was depressed in PRL immunization hens, developmental speed of large white follicles was found to be slower than in the BSA-immunized control hens ( P < 0.05). These results indicate that immunization against PRL slows down ovarian follicular development and reduces hen egg-laying performance, suggesting that PRL plays a stimulatory role in ovarian follicular development in chicken hens.

Can differences in incubation patterns of Common Redshanks Tringa totanus be explained by variations in predation risk?

The effects of predation on Common Redshanks Tringa totanus incubation patterns and behaviour was investigated in 2006 and 2007 at three mainland study sites at the Jadebusen and at one study site on the island Wangerooge, Wadden Sea National Park Lower Saxony (Germany), using temperature data loggers. At these sites, breeding Redshanks were naturally exposed to different predation pressures (as revealed by different hatching success) that varied between 10 and 90% amongst study sites. In areas with a higher predation risk, incubating Redshanks showed a lower nest attendance than in areas where predation risk was low. On the mainland, two behavioural strategies could be distinguished. Some nests were unattended during the night for several hours whereas other nests were incubated for most of the night. Nocturnal absence behaviour was found only on the mainland, and then only in areas easily reached by ground predators. Since ground predators are often active during the night, and dangerous for the incubating birds, this behaviour has probably become established to avoid direct mortality of adult birds rather than avoidance of egg predation. This results from a trade-off between current and future reproduction. By leaving the nest unattended during the night, these birds probably put their own survival before reproduction to maximise their lifetime reproductive success. Since such long incubation recesses may have negative consequences for embryo development, the results of this investigation provide an example of an indirect effect of predation. However, the behavioural trait of nocturnal absence from the nest may directly reduce reproduction and thus fitness of these individuals.

Respiratory morphology of the Abedus herberti Hidalgo egg chorion (Hemiptera: Belostomatidae)

Although giant water bugs (Hemiptera: Belostomatidae) are large, aquatic insects known for their obligate paternal egg brooding behaviors, little research has focused on the structure of their eggs. The respiratory requirements of developing embryos likely created selection for brooding, so a thorough understanding of the respiratory morphology of belostomatid eggs could help explain how brooding behaviors facilitate embryonic gas exchange. This study used scanning electron microscopy to document the respiratory microstructure of the eggs of Abedus herberti, a back brooding giant water bug. The exochorion is similar to that of other belostomatids in texture and organization except that the respiratory region is confined to the uppermost quarter of the egg. This is the area exposed to the atmosphere by encumbered males. A plastron network made up of densely packed vertical projections demarcates the boundary between the respiratory and nonrespiratory regions of the chorion. The internal chorion is composed of alternate air-filled and denser layers that likely facilitate the movement of oxygen from the aeropyles at the top of the eggs to the developing embryonic tissues. J. Morphol., 2011. © 2011 Wiley-Liss, Inc.

Date of Nest Initiation Mediates Incubation Costs of Wood Ducks (Aix Sponsa)

Incubation has a significant reproductive cost in birds that can limit both current and future reproductive success. We manipulated the incubation period of Wood Ducks (Aix sponsa) to examine how female body mass, incubation behavior, and nest temperature responded to changes in incubation costs. We found no relationships between the length of the incubation period and either the percent loss of body mass or the body mass at the end of incubation. However, females that initiated nests early in the season lost more body mass than females that nested later. The number of daily recesses increased slightly with longer incubation periods, but incubation constancy over the full incubation period and during the last week of incubation was not affected by incubation-period length. Variation in incubation constancy was explained best by nest initiation date. Incubation constancy was greatest for early-nesting females and declined for females that nested later. There also was a weak positive relationship between body mass and incubation constancy. Average nest temperature was not associated with the length of the incubation period but increased with increasing incubation constancy and as the breeding season progressed. Evidence from this study is consistent with the idea that incubation is an important reproductive cost that may constrain the timing of nest initiation in Wood Ducks. Poor-quality females, by delaying nest initiation, experienced reduced incubation costs and were able to maintain nest temperatures at levels similar to those of early-nesting females.

High resolution patterning of sapphire by F2-laser ablation

The ablation behavior of single crystalline sapphire with nanosecond laser pulses at 157 nm wavelength is investigated. Ablation rates of about 10 to 100 nm/pulse are obtained at fluences ranging from 1 to 9 J/cm2. At moderate fluences, incubation behavior is observed, i.e. ablation starts after material modification by a number of laser pulses. The ablation can be utilized to fabricate sapphire micro-optics. The capability of creating lenses or gratings on the tip of sapphire fibers is demonstrated. Multilevel diffractive optical elements and high resolution gratings with 1 μm period are fabricated on planar sapphire substrates.