Egg coloration and selection for crypsis in open-nesting blackbirds

High variation in egg coloration among birds has traditionally been explained as adaptation for camouflage. We tested this hypothesis by conducting reciprocal clutch exchanges (n=301) among Brewer's blackbirds Euphagous cyanocephalus , red-winged blackbirds Agelaius phoeniceus , and yellow-headed blackbirds Xanthocephalus xanthocephalus . We predicted that clutches placed against their natural nest backgrounds would have higher survival rates than heterospecific clutches. Intraspecific clutch exchanges were used as a control. Clutch survival was monitored for a 9-d period at all nests, during which time incubation rhythm and nest defense were quantified. Intraspecific clutch exchanges did not influence incubation or nest defense. For two of the species, intraspecific clutch exchanges did not influence clutch survival; in red-winged blackbirds, however, intraspecifically exchanged clutches had somewhat depressed survival curves relative to control clutches (P=0.08). The effect of interspecific clutch exchanges differed by host species. In Brewer's nests, eggs of the yellow-headed blackbird had lower survival than Brewer's eggs (P=0.02), but survival of red-winged blackbird eggs did not differ from Brewer's eggs (P=0.50). In nests of red-winged blackbirds, all three clutch types had approximately equal survival. In yellow-headed blackbird nests, eggs of the red-winged blackbird had lower survival than yellow-headed blackbird eggs (P=0.06), and survival of Brewer's eggs did not differ from yellow-headed blackbird eggs (P=0.31). These findings support a role for egg coloration as camouflage in two of the three species studied.     

Antibodies to Ockelbo virus in three orders of birds (Anseriformes, Galliformes and Passeriformes) in Sweden.

Sera from 324 birds collected in an Ockelbo virus disease endemic area in central Sweden were examined for the presence of specific antibodies to Ockelbo virus by a plaque reduction neutralization test. Birds examined belonged to the orders Anseriformes (n = 207), Galliformes (n = 66) and Passeriformes (n = 51). Ockelbo virus neutralizing antibodies were detected in 26 (8%) of the specimens, including species from each of the three orders tested. Specific antibodies found in caged birds and in 6- to 10-week-old birds suggested local transmission. The highest antibody prevalence (27%, 14/51) was observed in the Passeriformes in which 5 of 9 species tested contained antibodies. The high antibody prevalence in passeriforms and the very large population of this group in relation to other avian groups in Sweden gives them a high potential as amplification hosts for Ockelbo virus.     

Egg crypsis and clutch survival in three species of blackbirds (Icteridae)

For most open-nesting passerine birds, the primary function of egg pigmentation is crypsis. Interspecific variation for egg coloration is quite high, even among species that nest in the same locale. This variation might be maintained by selection to blend into species-specific nest cups, which vary in pattern because they are constructed from different materials. To test this hypothesis we photographed 30 clutches of Brewer's blackbirds ( Euphagus cyanocephalus ), 26 clutches of red-winged blackbirds ( Agelaius phoeniceus ), and 24 clutches of yellow-headed blackbirds ( Xanthocephalus xanthocephalus ), and quantified crypsis in terms of pattern (PD crypsis), brightness (MB crypsis) and brightness disparity (BD crypsis). The species were equally cryptic in terms of pattern crypsis, but differed significantly ( P < 0.01) in MB and BD crypsis. Intraspecific variation in pattern crypsis was surprisingly high. Mean clutch pattern disparity was highly correlated with mean background pattern disparity ( r = 0.999); this suggests selection for disparity matching, rather than for crypsis. We also monitored 25 clutches (7 Brewer's, 9 red-winged, and 9 yellow-headed blackbirds) for a 9-day period to determine if survival was related to crypsis. For Brewer's and yellow-headed blackbirds, successful nests were no more cryptic than failed nests. For red-winged blackbirds, there was a tendency ( P = 0.1) for less cryptic clutches to have higher survival; in addition, successful red-winged blackbird clutches had significantly ( P < 0.05) higher egg pattern disparity and background pattern disparity. Red-winged blackbird clutches are not concealed by overhanging vegetation, and high pattern disparity may enable them to blend into a large-scale heterogeneous background.     

Analyses of mitochondrial DNA nest ratite birds within the Neognathae: supporting a neotenous origin of ratite morphological characters

It is commonly acknowledged that the basal divergence among extant birds is between Palaeognathae and Neognathae. However, recent analyses of mitochondrial sequences have challenged that notion. In order to investigate this fundamental phylogenetic question, the complete mitochondrial DNA (mtDNA) molecule of the rook Corvus frugilegus (Passeriformes) was sequenced and included in phylogenetic analyses with the previously reported complete mtDNAs of the chicken Gallus gallus (Galliformes) and two ratite species, the ostrich Struthio camelus and the rhea Rhea americana (Struthioniformes). The analyses reconstructed a split between Passeriformes and a branch including Galliformes and Struthioniformes. Thus, the result is inconsistent with the traditional understanding of a basal avian divergence between Palaeognathae and Neognathae. The findings suggest that the morphological characteristics of the ratites are secondarily acquired, probably through neoteny and that the ratites are descendants of flying, neognathous ancestors.     

Succinic Dehydrogenase Distribution in the Pectoralis Muscle of Several East African Birds

The distribution of succinic dehydrogenase activity was investigated in the pectoralis muscle of thirteen East African birds, representing five Orders. It was found that the pectoralis muscle of the most primitive birds studied (Galliformes) contained all “white” muscle fibres whereas the more advanced birds (Passeriformes) had all “red” muscle fibres. Intermediate Orders had mostly a mixture of red and white muscle fibres. There also appeared to be a direct relationship between body size and average muscle fibre size. However, it was concluded that the most important factor in relation to the muscle structure is the bird's mode of flight. The relationship with the degree of evolution and body size only held true in so far as the birds which had developed the facility for sustained flight, by increasing their red muscle fibre content, were also smaller in size and constituted the more “evolved” Orders of birds. In support of this it was noted that migratory birds (i.e. engaging in sustained flight) from more primitive Orders also had a high red muscle fibre content in their pectoralis muscles.     

Simplified elimination of rabbit anti-rat acute phase protein IgG that shows cross reactivity with albumin

Antibody preparations against rat acute phase proteins were tested for cross reactivity with other serum proteins, including rat albumin. Rabbit anti-rat a alpha1-acid glycoprotein and ceruloplasmin IgG purified on protein A-Sepharose did not show any cross reactivity with rat albumin, hemoglobin or transferrin. Rabbit anti-rat haptoglobin and -macroglobulin IgG purified on protein A-Sepharose showed a 39% and 30% cross reactivity with rat albumin and a 20% and 19% cross reactivity with rat hemoglobin. Because these proteins in whole serum were not adsorbed on Cibacron Blue F3-GA Sepharose, the albumin would be adsorbed on Cibacron Blue F3-GA Sepharose by the use of whole rat serum. Rabbit anti-rat haptoglobin and alpha2-macroglobulin IgG showing cross reactivity with albumin was simply eliminated.     

Antiviral activity of ovotransferrin discloses an evolutionary strategy for the defensive activities of lactoferrin.

Ovotransferrin (formerly conalbumin) is an iron-binding protein present in birds. It belongs to the transferrin family and shows about 50% sequence homology with mammalian serum transferrin and lactoferrin. This protein has been demonstrated to be capable of delivering iron to cells and of inhibiting bacterial multiplication. However, no antiviral activity has been reported for ovotransferrin, although the antiviral activity of human and bovine lactoferrins against several viruses, including human herpes simplex viruses, has been well established. In this report, the antiviral activity of ovotransferrin towards chicken embryo fibroblast infection by Marek's disease virus (MDV), an avian herpesvirus, was clearly demonstrated. Ovotransferrin was more effective than human and bovine lactoferrins in inhibiting MDV infection and no correlation between antiviral efficacy and iron saturation was found. The observations reported here are of interest from an evolutionary point of view since it is likely that the defensive properties of transferrins appeared early in evolution. In birds, the defensive properties of ovotransferrin remained joined to iron transport functions; in mammals, iron transport functions became peculiar to serum transferrin, and the defensive properties towards infections were optimised in lactoferrin.     

Size and structure of the bird genome--I. DNA content of 48 species of Neognathae

The nuclear DNA content was evaluated in 48 species of Neognathae birds belonging to 13 orders, namely Anseriformes, Charadriiformes, Columbiformes, Ciconiiformes, Falconiformes, Galliformes, Gruiformes, Passeriformes, Pelicaniformes, Phoenicopteriformes, Piciformes, Psittaciformes and Strigiformes. The DNA content, expressed in pg/nucleus, ranges from 2.81 to 4.97. The genome size variability within and among families is discussed on the basis of the Hinegardner's (1976) model of genome evolution.     

Comparative histology, histochemistry and innervation of striated muscle fibers of the greater pectoralis muscle and supracoracoid muscle in birds

The morphology of the pectoralis major muscle and the supracoracoideus muscle was compared in three Galliformes and five Passeriformes, in relation to partial behavioral characteristics. In all species, two fibres types are observed. The frequencies of these fibres are different, especially between Galliformes and Passeriformes, but also between Coturnix and other Galliformes. All fibres show phasic innervation. A relation of the extent between synaptic gutters and muscle activity is suggested.     

Sciatin Is a Transferrin-Like Polypeptide

Abstract: Sciatin, an acidic glycoprotein from chicken sciatic nerve, has myotrophic effects on avian skeletal muscle cells in culture. As sciatin was found to have certain structural similarities to transferrin, we further investigated the physicochemical characteristics of sciatin in order to determine the relationship between these two proteins. Sciatin was found to be strikingly similar to ovotransferrin in amino acid composition. In addition, amino acid sequence analysis revealed that sciatin and ovotransferrin had identical amino-terminal sequences for at least the first 20 amino acid residues. Chicken ovotransferrin, but not human serum transferrin, cross-reacted with rabbit antisciatin antibodies upon rocket immunoelectrophoresis and double immunodiffusion in agar. In addition, in the presence of bicarbonate, sciatin bound approximately 2 mol ferrous iron/mol protein. Using the purification procedure developed for sciatin, we purified a protein from chicken serum that cross-reacted with antisciatin serum, migrated at a position identical to that of sciatin or ovotransferrin on two-dimensional gel electrophoresis, had an amino composition very similar to ovotransferrin and sciatin, and had myotrophic effects on cultured muscle cells. From these data, we conclude that sciatin is a growth-promoting polypeptide closely related in structure to transferrin.     

The developmental origin of zygodactyl feet and its possible loss in the evolution of Passeriformes

The zygodactyl orientation of toes (digits II and III pointing forwards, digits I and IV pointing backwards) evolved independently in different extant bird taxa. To understand the origin of this trait in modern birds, we investigated the development of the zygodactyl foot of the budgerigar (Psittaciformes). We compared its muscular development with that of the anisodactyl quail (Galliformes) and show that while the musculus abductor digiti IV (ABDIV) becomes strongly developed at HH36 in both species, the musculus extensor brevis digiti IV (EBDIV) degenerates and almost disappears only in the budgerigar. The asymmetric action of those muscles early in the development of the budgerigar foot causes retroversion of digit IV (dIV). Paralysed budgerigar embryos do not revert dIV and are anisodactyl. Both molecular phylogenetic analysis and palaeontological information suggest that the ancestor of passerines could have been zygodactyl. We followed the development of the zebra finch (Passeriformes) foot muscles and found that in this species, both the primordia of the ABDIV and of the EBDIV fail to develop. These data suggest that loss of asymmetric forces of muscular activity exerted on dIV, caused by the absence of the ABDIV, could have resulted in secondary anisodactyly in Passeriformes.     

GRASSLAND BIRD USE OF RIPARIAN FILTER STRIPS IN SOUTHEAST IOWA

Abstract: The U.S. Department of Agriculture (USDA) under its Continuous Enrollment Conservation Reserve Program (CRP) has actively promoted establishment of conservation buffers. Although these programs are intended to benefit wildlife in addition to protecting soil and water resources, benefits to grassland birds may be compromised by narrow widths, presence of woody vegetation, and high predation pressure. During 2001 and 2002, we surveyed breeding grassland birds and searched for nests in 33 CRP filter strips that varied in planting mixture (cool-season vs. warm-season grasses) and adjacent edge type (non-wooded vs. wooded). The most abundant species in filter strips were red-winged blackbird (Agelaius phoeniceus), dickcissel (Spiza americana), song sparrow (Melospiza melodia), and common yellowthroat (Geothlypis trichas). Relative abundances of birds and nests were similar between cool-season and warm-season planting mixtures. Dickcissels and red-winged blackbirds and their nests were relatively less abundant at wooded than non-wooded sites. Our nest success estimates generally were low in all treatments, and nest success varied little with the variables we studied. Predation was the major cause of nest failure; 62% of all nests were depredated. Although the most common birds using filter strips are generalists, filter strips also have potential to provide breeding habitat for some species of management concern.     

Comparative histology, histochemistry and innervation of the striated muscle fibers of the peroneus longus muscle

The morphology of the peroneus longus muscle was compared in three Galliformes and five Passeriformes in relation to partial behavioral characteristics. In the quail two fibre types are found, while the muscle of the other species is composed of three fibre types. The frequencies of these fibres are different, especially between Galliformes and Passeriformes. The peroneus longus muscle in the quail is innervated only from the phasic system. The other species show phasic and tonic innervation. There is a correlation between the muscle fibre calibre and the extent of the synaptic gutter.     

An updated list and some comments on the occurrence of intraspecific nest parasitism in birds

This paper presents a list, compiled from the literature, of bird species in which intraspecific nest parasitism (INP) occurs. INP was reported in 234 species: one Struthioniformes, two Tinamiformes, two Procellariiformes, six Podicipediiformes, five Ciconiiformes, one Phoenicopteriformes, 74 Anseriformes, one Falconiformes, 32 Galliformes, eight Gruiformes, 19 Charadriiformes, nine Columbiformes, five Cuculiformes, two Apodiformes, one Coraciiformes and 66 Passeriformes. Hence, INP is very common among precocial species, and less so among altricials. Irrespective of this, most INP birds are colonial.     

Molecular cloning of major histocompatibility complex class II B gene cDNA from the Bengalese finch Lonchura striata

The only avian major histocompatibility complex (Mhc) genes thus far identified are from species of the relatively small order of Galliformes, while by far the largest order of Passeriformes (songbirds), containing some 60% of extant bird species, has not been studied at all in this regard. The Galliformes emerged more than 55 million years (my) ago, the Passeriformes some 25 my ago. Because of the potential for the use of Mhc genes as markers in the study of songbird populations, an attempt was made to clone class II B genes of a passeriform species, the Bangalese finch Lonchura striata acuticauda. Using a set of primers designed on the basis of known sequences, a probe corresponding to part of exon II was obtained by the polymerase chain reaction. The probe was then used to screen a Bengalese finch cDNA library and to isolate and sequence two nearly full-length clones. The sequences reveal the presence of one presumably functional class II B locus in this bird species.     

Evolution of preproinsulin gene in birds

The coding region of the preproinsulin gene has been cloned and partly sequenced in a variety of marine and terrestrial birds (28 species). All genes showed the "ancestral" structure with a large intron-2. The size of intron-2 changed considerably during the evolution of birds (2.4-4.2kb). The hydrophobicity of signal peptides was conserved. Bird C-peptides were predicted to be 28 amino acids long, but circulating C-peptides would be only 26 amino acids long, with Passer as a possible exception. Bird C-peptides were found to lack the sequences identified in mammals as responsible for peptide bioactivity and the structure of the central part. In contrast, predicted insulin sequences were highly conserved. Only two types of analog were identified: the hypoactive form (GluA8), present only in Anseriformes and the hyperactive form (His A8), present in all other species. Based on 3'-nucleotide sequence analysis (extending into intron-2), birds appeared to be monophyletic. Five groups were clearly identified: Paleognathae, Galliformes, Anseriformes, Passeriformes, and Charadriiformes. Paleognathae were suggested as the basal group, supporting the traditional view of avian evolution. Subsequent branching identified a gallo-anserae group and a group containing all other Neognathae. Surprisingly, Columba livia (Columbiforme order) clustered with Galliformes. With represented species, Procellariiformes and possibly Ciconiiformes, and Pelicaniformes were suggested as paraphyletic, in agreement with conclusions from some studies based on mitochondrial DNA sequences.     

Evolutionary changes in color patches of blackbirds are associated with marsh nesting

Fully unraveling the mechanisms of sexual selection requiresan understanding of the variation in secondary sexual traitsacross species in a monophyletic assemblage and an understandingof the evolutionary relationships between those species. Therole of red and yellow male plumage coloration in territorydefense and sexual selection has been well studied in the red-winged blackbird (Agelaius phoeniceus), and males of many other close relatives of this species also have what appear to be carotenoid-pigmented patches in their plumage. We explored variation in male plumagecoloration across species of New World blackbirds (family Icteridae):traits known to be involved in sexual selection in this group.We document that blackbird lineages in which extant speciesbreed in marshes tend to have evolved from an all-black ancestralplumage to one exhibiting carotenoid plumage patches. The twomost likely hypotheses to explain this pattern are (1) increasedsexual selection intensity in marshes because of increasedvariance in territory quality and (2) increased frequency ofmale-male territorial interactions because of an increaseddensity of territories in marshes, but other hypotheses cannotbe ruled out. This pattern is consistent with either intersexualor intrasexual selection and warrants further investigation.     

Why brown-headed cowbirds do not influence red-winged blackbird parent behaviour

Brown-headed cowbirds, Molothrus ater, frequently parasitize red-winged blackbirds,Agelaius phoeniceus . The presence of a brood parasite, unrelated to both host nestlings and parents, has provoked speculation regarding within-brood food allocation and parental provisioning. This study is the first to compare directly the effect of brood parasitism on host parent and offspring behaviour in younger and older broods. We videotaped 28 unparasitized red-winged blackbird broods and compared them to 22 parasitized broods. Red-winged blackbird nestling begging appears largely unaffected by cowbird parasitism. The presence of the cowbird in the nest affected neither the latency nor duration of host nestling begging, but stimulated more frequent begging by red-winged blackbird nestlings following food distribution. Begging by cowbirds was unique in two ways: (1) cowbirds maintained a consistent begging effort throughout the nestling period (but did not receive a consistent food share); and (2) cowbirds begged longer and more frequently following the allocation of food. Persistent begging by the cowbird following the allocation of food has implications for the division of parental care, if by doing so the brood parasite is able to provoke the foster parent to increase provisioning, at the expense of brooding. We found no evidence for the adjustment of parental care. Neither the foraging rates nor the lengths of the parental feeding visits differed markedly between parasitized and unparasitized broods. Copyright 2003 Published by Elsevier Science Ltd on behalf of The Association for the Study of Animal Behaviour.      

Species specificity of transferein binding,endocytosis and iron internalization by cultured chick myogenic cells

Summary The ability of unlabelled heterologous transferrin to interact with transferrin receptors on developing chick myogenic cells was investigated by measuring their capacity to inhibit the surfacebinding and internalization of¹²⁵I-and⁵⁹Fe-labelled ovotransferrin. Transferrins from rat, rabbit, human, and a species of kangaroo (Macropus fuliginosus) were unable to inhibit either surfacebinding or internalization of labelled ovotransferrin even at concentrations ten times the molar concentration of the ovotransferrin. Transferrins isolated from the serum of a toad (Bufo marinus) and a lizard (Teliqua rugosa), when added at high concentrations, were found to reduce surface-binding of¹²⁵I-Tf by 20–25% but did not inhibit internalization of either¹²⁵I-Tf or⁵⁹Fe. This suggests that the effects of toad and lizard transferrins are due to non-specific binding to the myogenic cells. In contrast, inhibition of both surface-binding and internalization of labelled ovotransferrin was found when myogenic cells were incubated in the presence of the homologous transferrin (ovotransferrin). The species-specificity of transferrin binding, endocytosis and iron internalization did not vary with the state of proliferation or differentiation of the myogenic cells. However, the intracellular iron utilization was found to differ between differentiating presumptive and terminally differentiated myotubes. Internalized⁵⁹Fe was fractioned by gel filtration. In dividing and non-dividing presumptive myoblasts⁵⁹Fe was found to elute in three peaks, two with elution volumes corresponding to ferritin and transferrin and one at greater elution volume than that of myoglobin. In myotubes the same fractions occurred, and in addition some⁵⁹Fe was eluted at the same volume as myoglobin.Abbreviations Tf-Fe ₂ differic transferrin - BSA bovine serum albumin - BSS balanced salt solution - MEM Eagle's modified minimum essential medium - MW molecular weight - BUdR bromodeoxyuridine - Ara-C cytosine arabinoside