Blue Eggs Research Articles

Recognition and rejection of foreign eggs of different colors in Barn Swallows

Brood parasitic birds lay eggs in the nests of other birds, and the parasitized hosts can reduce the cost of raising unrelated offspring through the recognition of parasitic eggs. Hosts can adopt vision-based cognitive mechanisms to recognize foreign eggs by comparing the colors of foreign and host eggs. However, there is currently no uniform conclusion as to whether this comparison involves the single or multiple threshold decision rules. In this study, we tested both hypotheses by adding model eggs of different colors to the nests of Barn Swallows (Hirundo rustica) of two geographical populations breeding in Hainan and Heilongjiang Provinces in China. Results showed that Barn Swallows rejected more white model eggs (moderate mimetic to their own eggs) and blue model eggs (highly non-mimetic eggs with shorter reflectance spectrum) than red model eggs (highly non-mimetic eggs with longer reflectance spectrum). There was no difference in the rejection rate of model eggs between the two populations of Barn Swallows, and clutch size was not a factor affecting egg recognition. Our results are consistent with the single rejection threshold model. This study provides strong experimental evidence that the color of model eggs can has an important effect on egg recognition in Barn Swallows, opening up new avenues to uncover the evolution of cuckoo egg mimicry and explore the cognitive mechanisms underlying the visual recognition of foreign eggs by hosts.

Pheasant hatchability and physicochemical features of egg and extra-embryonic structures depending on eggshell color

The study aimed to analyze the biological value of eggs and extra-embryonic structures affecting pheasant hatchability depending on the eggshell's color. Eggs (1,415) from 62-wk-old pheasants were used. The quality of fresh blue (BL), brown (BR), and green (G) eggs were analyzed. Incubation lasted for 25 d. Thick albumen (d 0, 1, 7, 14), amniotic fluid (d 14, 18), and the yolk (d 0-14) were collected. The pH, viscosity, lysozyme activity, crude protein (CP) content in albumen and amnion, pH, vitelline membrane strength, and fatty acids (FA) content in the yolk were performed. The lowest hatchability was in the BL group, and the highest was in the G group. BL group showed lower eggshell thickness and strength and higher egg weight. In thick albumen and amniotic fluid, the pH decreased with the incubation. In the yolk, there was an increasing trend (P = 0.015), with a decrease on d 18 (P < 0.001). The vitelline membrane strength decreased after 1 d of incubation, excluding BR eggs (P < 0.001). Thick albumen viscosity was higher on d 14 in the G group than in other dates and groups, the lowest in amniotic fluid, and slightly higher in BL and BR eggs. On d 18, amniotic fluid viscosity increased (P < 0.001). The lowest viscosity was indicated in BL eggs (P < 0.001). The lysozyme activity in thick albumen on d 14 was the highest (uniquely in BR and G groups), and the lowest values were found in amniotic fluid on d 14; after four d, the activity increased (P < 0.001). The CP content was higher in the BL group on d 14. In amnion, on d 14, the CP content was the lowest (<1%) and increased on d 18 (P < 0.001). There was a higher FA content (especially UFA) in the G group and a decrease in FA content after d 14 (P < 0.001). It was found that eggs with green eggshells have the highest biological value, and blue eggs are the least useful for incubation.

Evidence for infection influencing survival of the freshwater copepod Salmincola californiensis, a parasite of Pacific salmon and trout.

We explore apparent infection of Salmincola californiensis arising during investigations involving this lernaeopodid copepod parasitic on Pacific salmon and trout Oncorhynchus spp. We noted occasional unusual coloration of adult female copepods collected from the wild. These females were bright blue and pink in contrast to the cream white coloration characteristic of the copepod. We also observed that similar color patterns developed under laboratory settings when copepod eggs were held for hatching. In paired egg cases, we found consistent hatching failure of blue and pink eggs and patterns in apparent disease development that would be consistent with both vertical and horizontal transmission. Attempts to identify the cause of the apparent infection using genetic methods and transmission electron microscopy were inconclusive. Iridovirus infection was initially suspected, but bacterial infection is also plausible. This apparent reduced hatching success of S. californiensis warrants further exploration as it could reduce local abundances. Given the potential importance of a disease impacting this copepod, a parasite that itself affects endangered and commercially important Pacific salmon and trout, future research would benefit from clarification of the apparent infection through additional sequencing, primer development, visualization, and exploration into specificity and transmission.

Refine localizations of functional variants affecting eggshell color of Lueyang black-boned chicken in the SLCO1B3

Table eggs with color-uniformity shell are visually attractive for consumers. Lueyang black-boned chicken (LBC) lays colorful eggs, which is undesirable for sale of table eggs, but provides a segregating population for mapping functional variants affecting eggshell color. SLCO1B3 was identified as the causative gene for blue eggs in the Dongxiang and Araucana chickens. The aim of this study is to map functional variants associated with chicken eggshell color in the SLCO1B3. Eggshell color of LBC (n=383) was measured using the L*a*b color space. SLCO1B3 was resequencing using a subset (n=30) of 383 samples. Linkage disequilibrium among 139 SNP was analyzed. Association of 16 SNP in the SLCO1B3 and 8 in CPOX, ALAS1, and ABCG2 genes with L*a*b were tested by a polygenic model (LMM) and a polygenic/oligogenic mixed model (BSLMM). Chromatin state annotations were retrieved from the UCSC database. Effect of SLCO1B3 variants distributed in mapping and upstream 1.6-kb regions on promoter activities were analyzed using dual-luciferase reporter assay. One hundred and thirty-nine variants maintained low linkage disequilibrium with 80% of r2 less than 0.226. Fifteen SLCO1B3 variants were significantly associated with a*, of which 1B3_SNP108 was showed the strongest association and the largest effect on a*. In the BSLMM, 1B3_SNP108 alone appeared in the Markov chain Monte Carlo as major variants in 100% of posterior inclusion probability. None of variants in CPOX, ALAS1, and ABCG2 were significantly associated with color indexes except that 2 ALAS1 variants were associated with L*. 1B3_SNP108 distributes in the Intron4 where 6 active enhancers and 1 ATAC island were enriched. However, 1B3_SNP108-containing constructs showed negligible activities in the reporter assay. No significant differences of activities between haplotypes were found for five 5'-deleted promoter constructs. The data recognizes 1B3_SNP108 as a valuable marker for breeding of eggshell color. Functional variants are localized in the region adjacent to the 1B3_SNP108 due to low linkage disequilibrium in the LBC. Our findings extend the role of SLCO1B3 from a causative gene for blue eggs to a major regulator driving continuous variation of LBC eggshell color.

Brood parasitism and egg recognition in three bunting hosts of the cuckoos.

Comparative studies of egg recognition and rejection between various sympatric hosts provide insight into the coevolutionary history of the hosts and parasites, as well as the degree of antagonism between the species. Although buntings are widely considered to be a suitable host taxon for cuckoos, there has been relatively little research on this example of parasitism and host antiparasitic behaviour. Here we provided the first report on brood parasitism and egg recognition in three sympatric ground-nesting bunting hosts of the common cuckoo (Cuculus canorus), namely the yellow-throated bunting (Emberiza elegans), south rock bunting (E. yunnanensis), and crested bunting (E. lathami). The results show that for the five breeding seasons during 2018-2022, the parasitism rate by common cuckoos was 0.87% and 0.45% in yellow-throated buntings and south rock buntings, respectively, whereas the parasitism rate by an unidentified parasite was 4% during 2018-2023 in the crested bunting. The rejection rates of the three bunting hosts for blue non-mimetic eggs were 89.3%, 88.9%, and 100% for yellow-throated buntings, south rock buntings, and crested buntings, respectively. The rejection rates for red non-mimetic eggs by yellow-throated buntings and south rock buntings were lower at 76.9% and 82.4%, respectively. All three sympatric bunting hosts examined had high levels of egg recognition and egg rejection, suggesting that it may have been subjected to high parasitic history and that egg recognition ability was retained after the loss of parasitism, which needs to be further verified by future experiments.

Genetics and breeding of a black-bone and blue eggshell chicken line. 3. Visual eggshell color and colorimeter parameters in 3 consecutive generations

The BG line, originated by crossing 2 Chinese indigenous breeds, Dongxiang blue eggshell and Jiangshan black-bone, has been bred for black carcass and blue-greenish eggs. Aiming to study the genetic parameters and selection aspects of these eggshell colors, the 4 colorimeter parameters (L*, a*, b*, SCI=L*-a*-b*) were measured on ∼5 eggs/hen/age (200 d and 300 d) from each hen in 3 generations (G4=452, G5=508, G6=498). Visual eggshell color was classified as either "Light," "Blue," "Green," or "Olive," and data from G4 and G5 indicated that visual eggshell color was more accurately determined by combining the classifications of single representative egg/hen by 4 independent observers. Based on the apparent gradual variation in visual color, the 4 colors were expressed numerically (Light=1, Blue=2, Green=3, Olive=4) and the averages of the 4 observers (AveObs) were used as quantitative expression of the visual color of each egg. This expression, in the range from Blue to Olive, was highly significantly correlated with L*, b* and SCI. The a* values were also associated with AveObs, but not linearly; AveObs between 2 (Blue) and 3 (Green) had lowest a*, and it increased as AveObs was more Light (<2) or more Olive (>3). The heritability estimates of the colorimeter parameters were mostly very high; those of b* and SCI ranged between 0.7 and 0.8, and those of L* and a* between 0.6 and 0.7, indicating that they can serve as criterions to select for blue and/or green eggshells. The phenotypic and genetic correlations between the colorimeter parameters were highly significant and favorable. It is suggested that effective breeding for blue eggs can be done by selecting hens laying eggs with highest SCI/L* or lowest b* (against green and olive shades), followed by selection for low a* (against light shades). Breeding for green eggs can be done by selecting hens laying eggs with SCI ≈ 75 and/or L* ≈ 80 and/or b* ≈ 12. Breeding for hens that lay either blue or green eggs can be done by selection for low a* values.

Decision rules for egg-color-based rejection by two cavity-nesting hosts of the brown-headed cowbird.

Hosts of obligate avian brood parasites often evolve defense mechanisms to avoid rearing unrelated young. One common defense is egg rejection, for which hosts often rely on eggshell color. Most research has assumed that hosts respond to perceived color differences between their own eggs and parasite eggs regardless of the particular color; however, recent experiments have found that many hosts respond more strongly to brown foreign eggs than to equally dissimilar blue eggs. Yet, none of these prior studies tested a brown-egg-laying species and, with only one exception, all were conducted in open nests where light levels are considered sufficient for effective color-based egg discrimination. Here, we explored how two cavity-nesting hosts of the parasitic brown-headed cowbird (Molothrus ater) - the blue-egg-laying eastern bluebird (Sialia sialis) and the brown-egg-laying house wren (Troglodytes aedon) - respond to experimental eggs painted six distinct colors ranging from blue to brown. Rejection responses of both hosts were best predicted by perceived differences in color between the model egg and their own eggs. Specifically, we found that house wrens preferentially rejected eggs bluer than their own eggs. However, although we found that bluebirds relied on perceived differences in color for their egg rejection decisions, further tests are needed to determine whether they preferentially rejected brown eggs or simply responded to absolute perceived differences in color. These findings demonstrate that these cavity-nesting birds treat perceived color differences in distinct ways, which has important implications on the coevolutionary arms races and the interpretation of avian-perceived color differences.

The phenology and clutch size of UK Blue Tits does not differ with woodland composition

The deciduous tree‐herbivorous caterpillar‐insectivorous bird food chain is a well‐studied system for investigating the impacts of climate change across trophic levels. To date, across Europe, most attention has focused on the impacts of increasing spring temperature on changes to phenology in Oak‐dominated (Quercus spp.) woodlands. Paridae species and Pied Flycatcher Ficedula hypoleuca are the most studied secondary consumers, all of which demonstrate an advancement in reproductive phenology with increases in spring temperature. Shifts in climate and phenology may also impact on reproductive investment in clutch size, and the effects of climate on phenology and clutch size may vary depending on woodland composition. To date, the effects of among‐habitat variation in phenology and reproductive investment have received little attention. Insectivorous birds inhabiting woodlands that differ in tree composition may differ in the timing of breeding, due to local tree leafing phenology acting as a cue for egg‐laying date and/or clutch size. Moreover, for most insectivorous birds, woodland composition within a territory is likely to be the main determinant of food availability for both adults and chicks. Consequently, if warming springs affect the temporal patterns of food availability differently across different woodland compositions, this may affect the optimal average local phenology for nesting birds. Here, using data from 34 long‐term (mean 15 years) nest monitoring sites across the UK, we investigate the effect of woodland tree composition and temperature on Blue Tit Cyanistes caeruleus first egg date (FED) and clutch size. We supplemented the nest monitoring data by quantifying woodland composition, at a site level, through modified point counts. We predict that birds breeding in woodlands with greater proportions of late‐leafing species, such as Oak and Ash Fraxinus excelsior, will breed later than those breeding in woodlands with greater proportions of early‐leafing species, such as Birch Betula spp. and Beech Fagus sylvatica. We found no evidence for differences in Blue Tit FED or clutch size in relation to the proportion of any of the tree species investigated, after controlling for temperature and latitude (FED: −3.4 and 2.2, clutch size: −0.4 and − 0.2 eggs for one‐unit increase in temperature and latitude, respectively). In recent decades and across all sites, clutch size has decreased as spring temperatures have increased, a strategy which could allow birds flexibly to adjust their breeding phenology such that nestling demand coincides with peak food availability. The lack of an effect of woodland composition on Blue Tit phenology suggests Blue Tits do not fine‐tune their reproductive phenology to the local tree composition. Whether this lack of evidence for phenological divergence is due to an absence of divergent selection on breeding phenology and clutch size or to gene flow is not clear.

Examining causes and characteristics of egg ejection behaviour in the American robin (Turdus migratorius)

Abstract American robins (Turdus migratorius) are among few hosts of parasitic brown-headed cowbirds (Molothrus ater) that frequently eject foreign eggs from their nests. However, we know little about some characteristics of the robins’ egg ejection process including its distance and direction. We used a novel technique (i.e., radio transmitters inserted into 3D-printed eggshells) to examine egg rejection in female robins as a function of model egg coloration (i.e., robin-mimetic blue, non-mimetic deep blue, and non-mimetic beige). Based on prior work, we predicted that female robins’ egg ejection decisions would be dependent on egg coloration. Accordingly, we found a significant effect of female identity (using nest identity as a proxy) and model egg colour on egg ejection, but neither predicted ejection distance or direction. Deep blue model eggs had shorter ejection latencies than beige eggs. Fully characterizing the egg ejection process will allow us to further understand the mechanisms and outcomes of egg ejection behaviours in host-parasite interactions.

Experimental evidence that cuckoos choose host nests following an egg matching strategy.

The arms race between brood parasites and their hosts provides a classic model to study coevolution. Hosts often reject the parasitic egg, and brood parasites should therefore select host nests in which the colour of the eggs best matches that of their own. Although this hypothesis has received some support, direct experimental evidence is still lacking. Here, we report on a study of Daurian redstarts, which show a distinct egg-colour dimorphism, with females laying either blue or pink eggs. Redstarts are often parasitized by common cuckoos, which lay light blue eggs. First, we showed that cuckoo eggs were more similar in spectral reflectance to the blue than to the pink redstart egg morph. Second, we report that the natural parasitism rate was higher in blue than in pink host clutches. Third, we performed a field experiment in which we presented a dummy clutch of each colour morph adjacent to active redstart nests. In this set-up, cuckoos almost always chose to parasitize a blue clutch. Our results demonstrate that cuckoos actively choose redstart nests in which the egg colour matches the colour of their own eggs. Our study thus provides direct experimental evidence in support of the egg matching hypothesis.

Quantitative analysis of CRISPR/Cas9-mediated provirus deletion in blue egg layer chicken PGCs by digital PCR

Primordial germ cells (PGCs), the precursors of sperm and oocytes, pass on the genetic material to the next generation. The previously established culture system of chicken PGCs holds many possibilities for functional genomics studies and the rapid introduction of desired traits. Here, we established a CRISPR/Cas9-mediated genome editing protocol for the genetic modification of PGCs derived from chickens with blue eggshell color. The sequence targeted in the present report is a provirus (EAV-HP) insertion in the 5’-flanking region of the SLCO1B3 gene on chromosome 1 in Araucana chickens, which is supposedly responsible for the blue eggshell color. We designed pairs of guide RNAs (gRNAs) targeting the entire 4.2 kb provirus region. Following transfection of PGCs with the gRNA, genomic DNA was isolated and analyzed by mismatch cleavage assay (T7EI). For absolute quantification of the targeting efficiencies in homozygous blue-allele bearing PGCs a digital PCR was established, which revealed deletion efficiencies of 29% when the wildtype Cas9 was used, and 69% when a high-fidelity Cas9 variant was employed. Subsequent single cell dilutions of edited PGCs yielded 14 cell clones with homozygous deletion of the provirus. A digital PCR assay proved the complete absence of this provirus in cell clones. Thus, we demonstrated the high efficiency of the CRISPR/Cas9 system in introducing a large provirus deletion in chicken PGCs. Our presented workflow is a cost-effective and rapid solution for screening the editing success in transfected PGCs.

Quality of table eggs in relation to shell colour

The present study evaluated the quality of table eggs in relation to shell colour. The study was conducted on 60 table eggs with shells coloured white, green, blue and brown (15 eggs per colour) obtained from laying hens from the same backyard farm. The following external quality traits of table eggs were measured: egg weight, percentage of dirty and cracked eggs, egg width and length, egg shape index, eggshell colour, eggshell weight and percentage, and eggshell thickness. The following internal quality indicators of table eggs were determined: albumen weight and percentage, albumen pH value, albumen width, length and height, Haugh index, albumen index, yolk weight and percentage, yolk pH value, yolk width and height, yolk index and yolk colour. Green eggs had the lowest weight, as well as the lowest width and length. White eggs had the highest eggshell dirtiness scores and egg shape index, while brown eggs had the highest eggshell thickness and weight. Green and brown eggs had the highest albumen index and Haugh index. In addition, green eggs had the lowest yolk width and the highest yolk index. White eggs had the highest albumen and yolk width, the greatest albumen length and the lowest albumen height. Yolks of white and blue eggs had a higher sensory colour score, as well as lower L* and b* values compared to the yolks of green and brown eggs. Based on the results of this study, it can be concluded that green and brown table eggs are of better overall quality compared to white and blue table eggs.

Through Thick and Thin

Through Thick and Thin

Research Note: L*a*b* color space for prediction of eggshell pigment content in differently colored eggs

Eggshell color is the most intuitive external feature that affects consumer acceptance. Different eggshell colors are mainly determined by protoporphyrin IX and biliverdin content. The selection of eggshell color by the human eye with an eggshell color fan can be roughly classified. Although more technologically advanced, a colorimeter or spectrophotometer might be of limited use when observing a variety of shell colors, such as brown, olive, green, and blue. This study aimed to provide a convenient and accurate method for predicting the content of eggshell pigments by measuring eggshell color using the Commission International de L'Eclairage (CIE) L*a*b* system. The results showed the deepening of eggshell color in brown and blue eggs was correlated with increased eggshell pigment deposition, and eggshell color was significantly positively correlated with eggshell pigment content (P < 0.01). Furthermore, the adjusted R2 of the fitted function was in the range of 0.81 to 0.89, and the Spearman rank correlation coefficient between the predicted and true values was in the range of 0.89 to 0.93. In brief, the L*a*b* method of measuring eggshell color to predict the amount of eggshell pigment deposition is convenient, effective, and promising for layer production.

The Perceptual and Cognitive Processes That Govern Egg Rejection in Hosts of Avian Brood Parasites

Hosts of avian brood parasites are under intense selective pressure to prevent or reduce the cost of parasitism. Many have evolved refined egg discrimination abilities, which can select for eggshell mimicry in their parasite. A classic assumption underlying these coevolutionary dynamics is that host egg recognition depends on the perceivable difference between their own eggs and those of their parasite. Over the past two decades, the receptor noise-limited (RNL) model has contributed to our understanding of these coevolutionary interactions by providing researchers a method to predict a host’s ability to discriminate a parasite’s egg from its own. Recent research has shown that some hosts are more likely to reject brown eggs than blue eggs, regardless of the perceived differences to their own. Such responses suggest that host egg recognition may be due to perceptual or cognitive processes not currently predictable by the RNL model. In this perspective, we discuss the potential value of using the RNL model as a null model to explore alternative perceptual processes and higher-order cognitive processes that could explain how and why some hosts make seemingly counter-intuitive decisions. Further, we outline experiments that should be fruitful for determining the perceptual and cognitive processing used by hosts for egg recognition tasks.

Insights Into mRNA and Long Non-coding RNA Profiling RNA Sequencing in Uterus of Chickens With Pink and Blue Eggshell Colors

The blue egg is both of biological interest and economic importance for consumers, egg retailers, and scientists. To date, the genetic mechanisms underlying pigment have mainly focused on protein-coding genes. However, the underpinning mechanism of non-coding RNAs on the pigment deposition among different eggshell colors remains unknown. In this study, RNA sequencing was employed to profile the uterine gland transcriptome (lncRNA and mRNA) of 15 Changshun blue eggshell layers, to better understand the genetic mechanisms of deposition of blue eggshell color. Results showed that differentially expressed mRNAs, GO terms, and KEGG pathways among pink-eggshell and blue-eggshell chickens were mainly targeting immune- and transporter-related terms with the SLC family, IgJ, CD family, and MTMR genes. Furthermore, the progesterone-mediated oocyte maturation and cortisol synthesis and secretion pathway with targeted gene PGR and Pbx1 were significantly enriched between blue- and pink-eggshell chickens. Integrating analysis of lncRNA and mRNA profiles predicted 4 and 25 lncRNA–gene pairs by antisense and cis analysis. They were relative to immune, nerve, and lipids and amino acid metabolisms, porphyrin, and chlorophyll metabolism with targeted gene FECH and oxidative phosphorylation and cardiac muscle contraction pathways with targeted gene COX6A1. Within blue-eggshell chickens, the GO terms hindbrain tangential cell migration and phosphatidylinositol monophosphate phosphatase activity with targeted gene Plxna2 and MTRM1 were identified. Integrating analysis of lncRNA and mRNA profiles predicted 8 and 22 lncRNA–gene pairs. Most pathways were mainly enriched on lipid-related metabolisms as found in mRNA sequencing. The lncRNAs did exert similar functions in color formation by modulating pigment disposition and immune- and lipid-related metabolisms. Our results provide a catalog of chicken uterine lncRNAs and genes worthy of further studies to understand their roles in the selection for blue eggshell color layers.

Sperm numbers on the perivitelline layers of blue tit eggs are repeatable within a clutch, but independent of the occurrence of extra‐pair paternity

In many socially monogamous bird species, females produce offspring sired by males other than their social partner. A large body of research has aimed to elucidate the evolutionary causes and consequences of such extra‐pair paternity, but relatively little is known about the underlying behaviour. The number of sperm on the egg's perivitelline layers (PVL) is related to recent copulation activity and may thus give some insight into the female's mating behaviour. We used a simple technique that allowed us to remove embryonic cells from the blastoderm for DNA extraction whilst keeping the PVL intact for sperm counts. Using 243 eggs from 99 blue tits Cyanistes caeruleus, we show that PVL sperm numbers were repeatable within clutches (r = 0.40 [95% CI: 0.25–0.53]). However, neither overall sperm numbers nor changes in sperm numbers across the laying sequence differed between clutches that contained extra‐pair sired eggs and those that did not. Our results, therefore, provide no evidence that females with and without extra‐pair young differ in their copulation activity.

Cultivation and characterization of primordial germ cells from blue layer hybrids (Araucana crossbreeds) and generation of germline chimeric chickens

The chicken (Gallus gallus) is one of the most common and widespread domestic species, with an estimated total population of 25 billion birds worldwide. The vast majority of chickens in agriculture originate from hybrid breeding programs and is concentrated on few commercially used high performance lines, whereas numerous local and indigenous breeds are at risk to become extinct. To preserve the genomic resources of rare and endangered chicken breeds innovative methods are necessary. Here, we established a solid workflow for the derivation and biobanking of chicken primordial germ cells (PGCs) from blue layer hybrids. To achieve this, embryos of a cross of heterozygous blue egg layers were sampled to obtain blood derived and gonadal male as well as female PGCs of different genotypes (homozygous, heterozygous and nullizygous blue-allele bearing). The total efficiency of established PGC lines was 45% (47/104) within an average of 49 days until they reached sufficient numbers of cells for cryopreservation. The stem-cell character of the cultivated PGCs was confirmed by SSEA-1 immunostaining, and RT-PCR amplification of the pluripotency- and PGC-specific genes cPOUV, cNANOG, cDAZL and CVH. The Sleeping Beauty transposon system allowed to generate a stable integration of a Venus fluorophore reporter into the chicken genome. Finally, we demonstrated that, after re-transfer into chicken embryos, Venus-positive PGCs migrated and colonized the forming gonads. Semen samples of 13 raised cell chimeric roosters were analyzed by flow cytometry for the efficiency of germline colonization by the transferred PGCs carrying the Venus reporter and their proper differentiation into vital spermatids. Thus, we provide a proof-of-concept study for the potential use of PGCs for the cryobanking of rare breeds or rare alleles.

The time-activity budgets of breeding Blue Swallows Hirundo atrocaerulea and the effects of weather on nestling growth

The Blue Swallow is an intra-African migrant that breeds in its fragmented range from South Africa to southern Tanzania, from October to March annually. The birds migrate north and are on their non-breeding range in NE DRC, Uganda, NW Tanzania and W Kenya, from April to September annually. The global Blue Swallow population, estimated at <1 500 pairs, is classified as ‘Vulnerable’, because of its small and declining population. Only the female Blue Swallow incubates the eggs and broods the nestlings for the first nine days after they have hatched from the eggs. The growth rate of Blue Swallow nestlings is reduced by adverse weather conditions characterised by low temperatures (<14 °C), 3–4 consecutive days of fog and intermittent rainfall. In the Blue Swallow Natural Heritage Site (25°36′ S, 30°45′ E), food shortages, because of three or more consecutive days of adverse weather conditions resulted in Blue Swallows shifting entirely to self-maintenance by abandoning eggs and nestlings and attempting to breed again when weather conditions improved. The post-fledging survival of the nestlings affected by adverse weather conditions is reduced. The reason is that at the time of fledging the mass of these nestlings was below the mean mass of the adults and because the mass of nestlings developing under good weather conditions is equal to or greater than the mean mass of the adult birds. Circumstantial evidence suggests that Common Fiscal Lanius collaris may be the predator of Blue Swallow eggs and nestlings. Adult longevity and the breeding success of Blue Swallows may have been reduced by adverse weather affecting their entire meta-populations in the small and isolated patches of suitable habitat remaining for the birds. These characteristics of the Blue Swallow meta-populations may be contributing to their continued decline.

EARLY NEST RECORD AND ADDITIONAL NOTES ON THE BREEDING BIOLOGY OF THE CHESTNUT-CAPPED BRUSH-FINCH (ARREMON BRUNNEINUCHA SUTTONI) IN SOUTHERN MEXICO

The natural history and breeding biology of species in the genus Arremon (Passerellidae) remains incomplete. Here, we document an early nest record and provide additional notes on the breeding biology of the Chestnut-capped Brush-finch (Arremon brunneinucha suttoni) from the Sierra Madre del Sur in southern Mexico. We found one bulky, open cup nest with two pale blue eggs. The nest was found greater than one month prior to previous nest descriptions, suggesting a possible shift in breeding phenology. Future studies across the range of A. brunneinucha will help clarify our findings within the context of geographic variation in this species and possible causes.