SPECIES

Pink-footed Shearwater Ardenna creatopus Scientific name definitions

Ryan D. Carle, Valentina Colodro, Jonathan Felis, Joshua Adams, and Peter J. Hodum
Version: 2.0 — Published April 9, 2022

Breeding

Introduction

Breeding colonies are in steep, densely forested, high elevation areas (usually > 150 m) on Isla Mocha and forested or deforested/unvegetated areas from nearly sea level up to approximately 500 m elevation in the Juan Fernández Islands. Nests in subterranean earthen burrow, where a single egg is laid. Both parents provision the chick. Adults fly to and from colonies at dusk or at night, and are nocturnally active outside of burrows. The breeding period extends from October through May.

Phenology

The breeding period extends from arrival on breeding colonies in October and November (38), through chicks fledging, typically in late April through May (33, 4). Based on a full year of trail camera monitoring, the earliest dates of arrival at colonies were August 31 on Isla Robinson Crusoe (38) and September 17 on Isla Mocha (different years were monitored on each island) (Oikonos, unpublished data). Birds began to arrive in large numbers starting in October (38). Breeding is presumably timed to match periods of productive upwelling conditions in the Humboldt Current (65).

First Brood

Egg laying occurs during late November to early December. Chick hatching typically occurs in late January to early February, and chicks typically fledge from late April through May (33, 4, 38).

Second/Later Broods

Like other procellariiform seabirds, the species is not known to lay second or replacement clutches (66). In > 10 years of reproductive monitoring on each of the three breeding colonies, there has been no evidence of laying of replacement or second broods (Oikonos, unpublished data).

Nest Site

Selection Process

Little information. Birds are present in breeding colonies both inside and outside of burrows in October (38). Some adults will possess a burrow, but not breed that year (37).

Microhabitat

Nests exclusively in self-excavated earthen burrow (4). Microhabitat associated with the nest burrow varies among islands; see Habitat in Breeding Range for details.

Site Characteristics

Breeding colonies on islands off central Chile are generally on steep slopes in both open and forested habitats. See Habitat in Breeding Range for details.

Nest

Construction Process

Nests exclusively in self-excavated earthen burrow (4). Digs burrow with the bill, using feet to push excavated soil out of the burrow (PJH). No information on sex-specific nest building effort, though in similar species it is thought to be undertaken by the male, due largely to the earlier arrival of males at breeding colonies (67).

Structure and Composition

A simple nest chamber is typically found at the end of the burrow, with a circular nest scrape in the center of the chamber (PJH). In general, no nesting material is used, although some pairs include dried twigs and other vegetation in the rudimentary nest scrape (8).

Dimensions

Burrow length varies by colony, most likely due to the softness of substrate and ease of digging. Burrow length was characterized by Brooke (4) as "mostly > 2 m long." In rocky areas, burrows are generally shorter (e.g., approximately 1 m long on Isla Santa Clara), whereas burrows can be > 3 m long in soft soil (e.g., the Tierras Blancas colony in poorly-consolidated pyroclastic flow material on the east side of Isla Robinson Crusoe; 68; Oikonos, unpublished data).

Microclimate

No information.

Maintenance or Reuse of Nests

As in many Procellariids, site fidelity to nest burrows is presumably high (66). Unless damaged by erosion, burrows persist for many years (PJH) and are likely used by multiple generations of shearwaters, but there are no data on individual return rates to nests.

Nonbreeding Nests

Does not use nonbreeding nests.

Eggs

Shape

Mean (mm ± SD) dimensions of a sample of 11 eggs measured was 73.3 ± 2.72 × 48.2 ± 2.26 (69).

Mass

No information.

Eggshell Thickness

No information.

Color and Surface Texture

Egg is white, often becoming stained. Texture is matte (PJH).

Clutch Size

One egg.

Egg Laying

No information.

Incubation

Onset of Broodiness and Incubation in Relation to Laying

No information.

Incubation Patches

Both sexes have a single incubation and brood patch (PJH).

Incubation Period

Eggs are typically laid in late November through mid-December and hatching occurs in late January to February (4). No information on relative contribution of each sex to incubation. Bull (70) reported a mean incubation shift of 14 days.

Parental Behavior

No information.

Hardiness of Eggs Against Temperature Stress: Effect of Egg Neglect

Little information, although eggs that are left unattended during the day sometimes subsequently hatch (PJH).

Hatching

Hatching occurs from late January to February (4).

Preliminary Events and Vocalizations

No information.

Shell Breaking and Emergence

No information.

Parental Assistance and Disposal of Eggshells

No information on parental assistance. Eggs are sometimes ejected from burrows, but it does not appear that adults systematically remove eggshells after hatching (PJH).

Young Birds

Condition at Hatching

Chick weighs approximately 70–80 g and is covered in light gray down at hatching (PJH; see Appearance: Plumages). Mean mass of chicks between 1–5 days of age was 146 g (PJH). Chick is left unattended 1–3 days after hatching, with adults only returning for brief provisioning visits after the initial brood period (PJH).

Growth and Development

Limited information. For chicks measured at 11 nests, from hatching through day 41, postnatal growth was typical of shearwaters and followed a sigmoid model of growth (PJH). Chick remains in burrow and is fed by parents from hatching to fledging.

Sex Ratios and Sex Allocation

No information available.

Parental Care

Brooding

Adults brood young chick in first days of life; limited data suggest a typical brooding period of 1–3 days (PJH). No information on whether male and female share brooding duties.

Feeding

Both parents provision the chick from hatching to just before fledging, approximately early February to late April (29). The only information on feeding intervals is based on tracking of chick-rearing adults at Isla Mocha (29). Both parents returned to the nest during the chick-rearing period (29). Presumably, chicks were fed on each return. This assumption was supported by observations of adults that were captured before they entered burrows sometimes vomiting loads of food, whereas adults captured exiting burrows did not (RDC). Average foraging trip duration was 93.7 h ± 72.5 SD (3.9 d ± 3.0 SD) over three years (29). However, foraging trip duration was bimodal: average duration of “short” trips (defined as < 30 hours long with only one day at sea between nocturnal visits) was 18.6 h ± 3.0 SD (0.8 d ± 0.1 SD), and average duration of “long” trips (defined as > 30 hours long) was 121.2 h ± 65.9 SD (5.1 d ± 2.7 SD) (29). Foraging trip duration may sometimes be longer, as not all tagged birds in that study were recaptured before discontinuing tag recapture efforts (78% of tags deployed in that study were recaptured) (29). Each provisioning parent in a breeding pair usually arrived asynchronously, and often on different days (RDC), so the chick was fed more frequently than is accounted for by individual trip durations.

Nest Sanitation

No information.

Carrying of Eggs or Young

Not known to carry eggs or young.

Cooperative Breeding

Not reported.

Brood Parasitism by Other Species

Not reported.

Fledgling Stage

Departure from the Nest

Fledgling departs the nest at night from late April to early May (33, 4, 38). There is no evidence of chick returning to the nest after fledging.

Growth

No information.

Association with Parents or Other Young

No information.

Ability to get Around, Feed, and Care for Self

Sometimes exits the burrow before fledging to exercise wings (PJH).

Immature Stage

No information available after fledging; no juveniles have been tagged or tracked at sea.

Recommended Citation

Carle, R. D., V. Colodro, J. Felis, J. Adams, and P. J. Hodum (2022). Pink-footed Shearwater (Ardenna creatopus), version 2.0. In Birds of the World (P. G. Rodewald and B. K. Keeney, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.pifshe.02