Paulo E. Llambías

The design of artificial nestboxes for the study of secondary hole-nesting birds: a review of methodological inconsistencies and potential biases

Abstract. The widespread use of artificial nestboxes has led to significant advances in our knowledge of the ecology, behaviour and physiology of cavity nesting birds, especially small passerines. Nestboxes have made it easier to perform routine monitoring and experimental manipulation of eggs or nestlings, and also repeatedly to capture, identify and manipulate the parents. However, when comparing results across study sites the use of nestboxes may also introduce a potentially significant confounding variable in the form of differences in nestbox design amongst studies, such as their physical dimensions, placement height, and the way in which they are constructed and maintained. However, the use of nestboxes may also introduce an unconsidered and potentially significant confounding variable due to differences in nestbox design amongst studies, such as their physical dimensions, placement height, and the way in which they are constructed and maintained. Here we review to what extent the characteristics of artificial nestboxes (e.g. size, shape, construction material, colour) are documented in the ‘methods’ sections of publications involving hole-nesting passerine birds using natural or excavated cavities or artificial nestboxes for reproduction and roosting. Despite explicit previous recommendations that authors describe in detail the characteristics of the nestboxes used, we found that the description of nestbox characteristics in most recent publications remains poor and insufficient. We therefore list the types of descriptive data that should be included in the methods sections of relevant manuscripts and justify this by discussing how variation in nestbox characteristics can affect or confound conclusions from nestbox studies. We also propose several recommendations to improve the reliability and usefulness of research based on long-term studies of any secondary hole-nesting species using artificial nestboxes for breeding or roosting.

BREEDING DISPERSAL AND PHILOPATRY IN THE TREE SWALLOW

Abstract To study the patterns and determinants of philopatry and breeding dispersal in the Tree Swallow (Tachycineta bicolor) we analyzed the records of 356 males and 1459 females captured in more than one breeding year around Ithaca, New York. Of these captures, only 4% of male and 14% of female breeders dispersed to a new site for breeding. With our combination of intensive study areas in Tompkins County, New York, and the efforts of volunteer banders throughout New York and surrounding states, we could have detected dispersal in excess of 400 km from the initial breeding site. Randomization tests revealed, however, that breeders dispersed much shorter distances than they could have been detected. Detailed analyses of recaptures in Tompkins County showed that over a 22-km range of distances, the chances of dispersal to a new breeding site declined with the distance from the original breeding site. Females that failed to fledge any offspring were much more likely to disperse than females that reproduced successfully, and the probability of dispersal declined gradually with female age. The spatial scale in which swallows gather and process information appears to be much larger than for passerines that defend all-purpose territories. Dispersión Reproductiva y Filopatría en Tachycineta bicolor Resumen. Para estudiar los patrones y los determinantes de la filopatría y la dispersión reproductiva en Tachycineta bicolor analizamos los registros de 356 machos y 1459 hembras capturados en más de un año reproductivo en los alrededores de Ithaca, New York. De estas capturas, sólo el 4% de los machos y el 14% de las hembras reproductivas se dispersaron a un nuevo sitio de cría. Con nuestra combinación de áreas de estudio intensivas en el Condado de Tompkins, New York, y los esfuerzos de colaboradores voluntarios que anillaron aves a lo largo de New York y los estados circundantes, pudimos haber detectado eventos de dispersión a más de 400 km desde el sitio de cría inicial. Exámenes aleatorizados revelaron, sin embargo, que las aves reproductivas se dispersaron a distancias mucho más cortas que las que se podrían haber detectado. Análisis detallados de recapturas en el Condado de Tompkins mostraron que en un rango de distancias de 22 km, las probabilidades de dispersión a un nuevo sitio de cría disminuyeron con la distancia desde el sitio de cría original. Las hembras que fracasaron en la cría de pichones presentaron una probabilidad de dispersarse mucho mayor que las hembras que se reprodujeron exitosamente, y la probabilidad de dispersión disminuyó gradualmente con la edad de la hembra. La escala espacial a la que T. bicolor recoge y procesa información parece ser mucho más grande que la de aves paserinas que defienden territorios de uso múltiple.

Mating opportunities, paternity, and sexual conflict: paternal care in northern and southern temperate house wrens

Males are generally predicted to care less for their young when they have more additional mating opportunities, lower paternity, or when their mates care more. We tested these predictions using male provisioning as a proxy for paternal care in two temperate populations of house wrens (Troglodytes aedon) with divergent life histories. Males in the migratory, occasionally socially polygynous New York, USA (northern) population provisioned less when more local females were fertile. A similar relationship was only weakly supported in the resident, socially monogamous Buenos Aires Province, Argentina (southern) population, possibly due to the higher density of house wrens there. A relationship between male provisioning and level of paternity within the brood was supported in both populations, but in opposite directions: while males in the southern population provisioned less at broods containing more extra-pair young, males in the northern population provisioned such broods more, contradicting predictions. Males provisioned less when their mates provisioned more in both populations, in agreement with sexual conflict theory. Additionally, the populations both exhibited a positive relationship between male provisioning and nestling age, but differed in the direction of the relationships of male provisioning with date and brood size. Our results suggest that even within a species, life history differences may be accompanied by differences in the determinants of behavior such as paternal care.

Range contraction in the pampas meadowlark Sturnella defilippii in the southern pampas grasslands of Argentina

The Vulnerable Pampas meadowlark Sturn- ella defilippii (Family Icteridae) is a Neotropical grassland bird that suffered a severe population reduction and range contraction during the 20th century. Formerly dis- tributed across most of the pampas grasslands, it is now confined to the southern tip of its original range. There are small groups of wintering birds in southern Brazil, a small reproductive population in eastern Uruguay, and the main reproductive population occurs on the southern pampas grasslands of Argentina. In this paper we report the results of an extensive field survey of these southern pampas grasslands, carried out to estimate the pampas meadowlarks population size and to iden- tify the factors potentially responsible for its range con- traction. During the 1999 breeding season we surveyed a total of 296 sample locations (transects, randomly selected points, and sites checked for nesting site re-occupation).We found 66 reproductive groups of pampas meadowlarks. The minimum population size and extent of occurrence were estimated to be 28,000 individuals and 4,810 km 2 , respectively. This value repre- sents a range contraction of c. 30% compared to that estimated in a study carried out between 1992 and 1996. Pampas meadowlarks re-occupied natural grassland sites for nesting that were used in previous breeding seasons when these sites remained undisturbed. Habitat transformation appears to be the main factor causing the range contraction of the pampas meadowlark. We suggest that long-term monitoring of this population and its preferred habitat, the natural grasslands, is required in order to ensure the conservation of this species.

The structure and organization of song in Southern House Wrens (Troglodytes aedon chilensis)

AbstractStudies of birdsong across very broad geographic scales, such as between the north temperate zone and the tropics, provide special opportunities to understand the role of variable ecologies, life histories and mating pressures on song structure and organization. The problem is typically studied through comparative, cross-species analyses because few species have such broad distributions to encompass both regions. The House Wren is an important exception, having the widest distribution of any native songbird in the Americas, from Canada to Tierra del Fuego. Across this range, they manifest considerable variation in life history, mating systems and migration, but there is no systematic research on corresponding song variation. Here we provide a first detailed characterization of song structure and organization for Southern House Wrens (Troglodytes aedon chilensis) in western Argentina and provide preliminary comparisons to Northern House Wrens. Songs of Southern House Wrens contained two distinct sections: an introduction of broadband noisy, or harmonic, notes followed by a louder terminal section of tonal, frequency-modulated syllables with a mean of seven syllables and three syllable types per song. The syllable repertoire was large (28), mostly shared and used to construct very large song repertoires (up to 170 song types with no evidence of a ceiling), but much smaller repertoires of commonly produced song types (24). Males tended to repeat song types many times before switching (eventual variety) but, at times, sang with immediate variety. Compared to Northern House Wrens, there were differences in the detailed form of some notes and syllables as well as in the relative emphasis of the softer introduction versus louder terminal section of songs. In broader patterns of song construction, organization, delivery, and the size of syllable and song repertoires, the two populations were very similar. These patterns are discussed in light of differences in life history, mating and migration between them.ZusammenfassungGesangsstruktur und -organisation beim Südlichen HauszaunkönigTroglodytes aedon chilensis Untersuchungen von Vogelgesang über große Gebiete hinweg, zum Beispiel in der nördlichen gemäßigten Zone und in den Tropen, bieten besondere Gelegenheiten, die Rolle variabler Ökologie, Lebensgeschichte und Paarungsdruck hinsichtlich der Gesangsstruktur und -organisation zu verstehen. Dieses Problem wird typischerweise mit Hilfe vergleichender Analysen mehrerer Arten untersucht, da nur bei wenigen Arten das Verbreitungsgebiet so groß ist, dass es beide Regionen einschließt. Der Hauszaunkönig, der die weiteste Verbreitung aller in Amerika heimischen Singvögel aufweist (von Kanada bis Feuerland), stellt hier eine wichtige Ausnahme dar. Über dieses Gebiet hinweg zeigt die Art beträchtliche Variation in Lebensgeschichte, Paarungssystem und Zugverhalten, doch gibt es keine entsprechende systematische Forschung bezüglich der Variation im Gesang. Hier liefern wir eine erste detaillierte Beschreibung der Gesangsstruktur und -organisation bei Südlichen Hauszaunkönigen (Troglodytes aedon chilensis) in Westargentinien und stellen vorläufige Vergleiche mit Nördlichen Hauszaunkönigen an. Die Gesänge der Südlichen Hauszaunkönige bestanden aus zwei unterschiedlichen Abschnitten: einer Einleitung aus verrauschten oder harmonischen Breitbandnoten, auf die eine lautere Endsektion tonaler frequenzmodulierter Silben folgte, mit im Mittel sieben Silben und drei Silbentypen pro Gesang. Das Silbenrepertoire war umfassend (28), wurde zum großen Teil gemeinsam genutzt und zum Aufbau sehr großer Gesangsrepertoires verwendet (bis zu 170 Gesangstypen mit keinen Hinweisen auf eine Obergrenze). Die Repertoires häufig produzierter Gesangstypen waren allerdings viel kleiner (24). Männchen tendierten dazu, Gesangstypen viele Male zu wiederholen, bevor sie wechselten (letztendliche Gesangsvielfalt), zeigten zeitweise jedoch auch unmittelbare Gesangsvielfalt. Verglichen mit Nördlichen Hauszaunkönigen bestanden Unterschiede in der genauen Form einiger Noten und Silben sowie in der relativen Betonung der leiseren Einleitung relativ zur lauteren Endsektion der Gesänge. Die beiden Populationen ähnelten sich sehr in den allgemeinen Mustern von Gesangsaufbau, Organisation und Darbietung sowie in der Größe der Silben- und Gesangsrepertoires. Diese Muster werden im Hinblick auf Unterschiede in Lebensgeschichte, Paarungs- und Zugverhalten zwischen den Populationen diskutiert.

Breeding success and social mating system of the Bay-capped Wren-Spinetail (Spartonoica maluroides).

Abstract We studied breeding biology, parental roles, and social mating system of the Bay-capped Wren-Spinetail (Spartonoica maluroides), a habitat specialist furnariid, in the Argentinean pampas. We found 42 nests during 2004–2007, two during egg laying, 28 during incubation, and 12 with nestlings. Mean clutch size was 3.17 eggs (n  =  29), the incubation period was 13 days, and nestlings remained in the nest for 12 days before fledgling. Bay-capped Wren-Spinetails are socially monogamous; both males and females develop a brood patch and contribute to incubation, brooding, and provisioning of nestlings. Wren-Spinetails are unique among furnariids as they build an open cup nest with a few presenting a loose domed roof. Breeding success of Bay-capped Wren-Spinetails was higher (total probability of nesting success  =  0.508) than other species of sympatric passerines because of low nest predation and high nest survival rates during incubation and nestling rearing stages.

Parental Risk-Taking Behaviour and Nest Defence During the Nestling Rearing Stage in Northern House Wrens Troglodytes aedon

Abstract Risk-taking behaviour of short lived nesting birds is often explained in relation to the reproductive value of offspring (the reproductive value hypothesis) and the harm that the absence of parental care can cause to nestlings (risk of harm-to-offspring hypothesis). The reproductive value hypothesis predicts that the risk assumed by adults should increases with nestling age, whereas the risk of harm-to-offspring hypothesis predicts the opposite pattern. We assessed the risk-taking behaviour of nesting males and females Northern House Wrens, Troglodytes aedon, faced with a predation threat (plastic owl model) when rearing 3–4 and 10–12 days old nestlings. We used the time elapsed until parents first entered the nest-box as a measure of risk-taking behaviour and alarm calling rate as a proxy of nest defence. Females resumed sooner parental activities when exposed to the model when nestlings were young, supporting the risk of harm-to-offspring hypothesis. In contrast, the time lasted to resume parental duties by males did not differ between nestling ages. Alarm calling rate increased with the nestling stage, as predicted by the reproductive value hypothesis. We suggest that nesting House Wrens responded to both nestling requirements and to the reproductive value of the brood, assuming greater risks when nestlings are more vulnerable and a more intense nest defence when nestlings are older.

Parental Care in the Great Kiskadee

Abstract We studied parental care in the Great Kiskadee (Pitangus sulphuratus) in a suburban residential area in Buenos Aires Province, Argentina, from September through December, 1998. Our data suggest that the dominant breeding system of the Great Kiskadees on our study site is social monogamy. Both male and female were involved in territory defense, nest building, and feeding the young. The female alone incubated the eggs and brooded the nestlings. Male and female visitation rates to the nest during the nestling period were similar.

Kleptoparasitism in the Great Kiskadee

Abstract Kleptoparasitism has been extensively described for raptors and seabirds, but there are fewer observations for passerine birds. Here we describe several events of interspecific kleptoparasitism in the Great Kiskadee (Tyrannidae: Pitangus sulphuratus) in Buenos Aires, Argentina. Although interspecific kleptoparasitism has not been described previously for this species, we believe this foraging strategy is more common than expected for a passerine bird. The observations described in this paper are consistent with four of the six ecological conditions proposed by Brockmann and Barnard (1979).

Effect of conspecific alarm calls in the parental behaviour of nesting southern house wrens

Alarm calls are usually used to signal the presence of a threat to members of the same species and have been studied broadly in social foraging species. We analysed the effects of conspecific alarm calls on the parental behaviour of a territorial species, the southern house wrens (Troglodytes aedon musculus), during nestling stage. We compared the parental response of adults feeding 9–11-day-old nestlings when faced with conspecific alarm calls and with a control non-sympatric species’ song broadcast from a neighbouring territory. We measured the time required by parents to return to the nest (latency) when exposed to the stimuli and estimated parent’s nest visitation rate and mean visit duration. Parents took longer to resume parental activities when we broadcast a conspecific alarm call, but they did not modify their nest visitation rate or the mean visit duration. Heterospecific songs did not seem to affect parental behaviour. Our results suggest that nesting southern house wrens can use alarm calls uttered from neighbouring territories to assess the presence of a threat and adjust their parental behaviour accordingly.