Population and nesting habitat survey for Oreotrochilus chimborazo chimborazo

Bouzat, Juan 1 ; Cañas-Valle, Gustavo1

Published Aug 21, 2025 on Dryad. https://doi.org/10.5061/dryad.sn02v6xfj

Data files

Aug 21, 2025 version files 101.99 KB

Dryad_Raw_Data.docx

94.72 KB
README.md

7.27 KB

Abstract

The adaptive significance of group-living has promoted considerable debate about the potential role of environmental drivers in the evolution of coloniality. Nest aggregations may result as a plastic response of reproductive individuals to limited substrate availability and favorable environmental conditions for nesting (Limited Substrate Availability Hypothesis). However, few studies have demonstrated the direct role of environmental factors in promoting social aggregations. A population survey of Oreotrochilus chimborazo chimborazo (Chimborazo Hillstar), a hummingbird subspecies endemic to the Ecuadorian High Andes, resulted in the identification of 7 nesting aggregations and 13 solitary nests. Of a total of 74 active nests detected, most (82%) were found in reproductive colonies. Furthermore, nesting aggregations were consistently associated year-round with roosting groups of males and non-reproductive females, a unique case among birds. These findings challenge the widespread assumption that hummingbirds are highly competitive solitary nesters. The subsequent characterization of Chimborazo Hillstar nesting habitat revealed that wind speed, temperature, humidity, and landscape features associated with substrate availability, ground cover vegetation, and water represent environmental factors associated with nesting, consistent with the Limited Substrate Availability Hypothesis. However, a semi-natural “experiment” comparing occupancy of solitary nesting locations versus nesting aggregations revealed that only 45.5% of the sites available for solitary nesting showed individual active nests, significantly lower than the 95% expected by random simulations. In contrast, nesting aggregations consistently had multiple active nests at significantly higher frequencies than expected, producing broods across multiple reproductive seasons. These results suggest that other factors beyond those associated with the Limited Substrate Availability Hypothesis may play a role in the development of nesting/roosting aggregations in the Chimborazo Hillstar, emphasizing the importance of the interaction of environmental and social factors in driving coloniality in birds.

Access this dataset on Dryad
- This dataset is associated with the following Dryad files: Dryad_Raw_Data.docx and README_Dryad.md

Dataset associated with Cañas-Valle and Bouzat (2024) publication in Ornithology (Vol 142: 1-13), entitled "Ecological drivers of coloniality in Oreotrochilus chimborazo chimborazo (Chimborazo Hillstar), a hummingbird endemic to the High Andes of Ecuador."
See Materials and Methods section of Cañas-Valle and Bouzat (2024) for specific descriptions of methods used for the collection of the data reported here. https://doi.org/10.1093/ornithology/ukae063

Descriptions

Raw Data associated with the study published in Ornithology (2024)

Population survey raw data
Nesting survey data
Nesting and roosting survey of colonial aggregations
Avian checklists
Characterization of Chimborazo Hillstar habitat
1. Quantitative variables associated with ravines as potential habitat for O. c. chimborazo
2. Landscape survey of qualitative variables associated with O. c. chimborazo habitat
Data on semi-natural experiment comparing solitary vs aggregated nesting sites
1. Occupancy and Recurrency of “experimental” culverts for solitary nesting and nesting aggregations
2. Simulations for random assignment of individuals to solitarily and aggregated nesting sites

Population Survey Raw Data

Sampling Transects: Identifiers of sampling transects
Individuals (N): Number of active individuals detected at sampling transect
Replicates (rep): Number of sampling replicates at sampling transect
N/rep: Number of individuals detected per sampling replicate at a transect
Area (hectares): Sampling area surveyed (in hectares)
Density (N/hectare): Density estimates of area sampled at individual transect (expressed as number of individuals per area in hectares)

Nesting Survey Raw Data

Nest Aggregations, Solirtary Nests; Locations with No-Nests: Number of Localities (N) with Nest Aggregations, Solitary Nests and No-Nests.
Location ID: Identifiers of nesting localities
Nests: Number of nests detected at a locality

Nesting and Roosting Survey of Colonial Aggregations

Sampling Seasons: Sampling seasons for surveys of nesting aggregations
Nesting Sites Location ID: Identifiers of Locations of Nesting Sites
All Nests: Number of Total Nests detected at nesting locations
Active Nests: Number of Active Nests detected at nesting locations
Roost M/F: Number of Roosting Males (M) and Females (F) detected at nesting locations

Avian Checklists

Common name: Common Species Name
Species: Current scientific name of species
T1; T2; RT1; RT2; RT3; RT4; RT5: Identifiers of sampling transects
X: Represent check for detection of a species at a spceific sampling ttransect

Characterization of Chimborazo Hillstar Habitat

Quantitative Variables associated with Ravines as Potential Habitat for O. c. chimborazo

RAVINE: Ravine Transect Identifier (RT1-RT5)
-0m; -500m; 1000.; 1500m; 2000m: Sampling site at a Ravine Transect for measuring microhabitat conditions inside (IN) and outside (OUT) of ravine
Day: Day at which sampling variables were measured (Day 1; Day 2)
Hour: Time at which sampling variables were measured at a specific sampling site
IN/OUT: Location (IN: Inside Ravine; OUT: Outside Ravine) where quantitative variables of microhabitat conditions were measured
Wind: Quantitative variable associated with wind speed (measured in km/h)
Temp: Quantitative variable associated with temperature (measured in centigrades (C))
Humid: Quantitative variable associated with humidity (measured as percent of humidity (%))

Landscape Survey of Qualitative Variables associated with O. c. chimborazo Habitat

Location ID: Identifier of sampling location
Nesting: Nesting variable refers to location with no nests (Nest-n), solitary nests (Nest-1), and aggregated nests (Nest-mny)
Water: Ecological variable associated with water availability (Wat-y: water presence; Wat-n: no water)
Cover: Ecological variable associated with vegetation cover (Cov-y: vegetation cover; Cov-n: no cover)
Alpines: Ecological variable associated with the presence of Alpine flowers (Alp-y: Presence; Alp-n: Absence)
Chuquiragua: Presence (Chu-y)/Absence (Chu-n) of Chuquiragua Jussieui
Surface: Presence (Sur-y)/Absence (Sur-n) of solid surface as nesting substrate
Grazing: Presence (Gra-y)/Absence (Gra-n) of grazing animals (sheep, lamas, or vicunas)
Trash: Human Disturbance as indicated by evidence of human activity (Tra-Y: Human disturbance; Tra-n: no evidence of disturbance)

Data on Semi-Natural Experiment comparing Solitary vs Aggregated Nesting Sites_Data

Occupancy and Recurrency of “experimental” culverts for solitary nesting and nesting aggregations

Experimental Culverts: Experimental culverts for solitary nesting
Nesting Aggregations: Localities for nesting aggregations
Nesting:
Nests: Number of nests detected at Experimental Culverts and Nesting Aggregations
Occupancy: Occupancy describes sites without signs of nesting (empty), with either remnants of nests or fecal splats (signs), with old nests not firmily attached or without fresh feces (old), and nests with a brooding female or fresh feces (active).
Feces: Categories of relative use of nesting sites based on relative thickness of fecal splats (see Methods in Cañas-Valle and Bouzat 2024)
Recurrency: Signs of current (Yes) or historic (Historic) reuse of localities for nesting.
Roosting (Male; Female): Number of roosting Males and Females detected at Experimental Culverts and Nesting Aggregations

Simulations for Random Assignment of individuals to Solitarily and Aggregated Nesting Sites

Solitary: Solitary nesting locations
Colonial: Colonial nesting locations
Available Nesting Sites: Number of available nesting sites at Solitary and Colonial nesting locations
Observed Active Nesting: Observed number of Active Nests at Solitary and Colonial nesting locations
Expected Nesting: Expected number of Active Nesting sites at Solitary and Colonial nesting locations based on the random assignment of individuals observed at Solitary and Colonial nesting locations (based on simulations with 1500 replications)

Sharing/Access information

This dataset is associated with the following Dryad files: Dryad_Raw_Data.docx and README.md

The dataset presented here is associated with the study by Cañas-Valle, G.X. and J.L. Bouzat (2024), published in Ornithology (Ornithology, Volume 142, Issue 2, 1 April 2025, ukae063, https://doi.org/10.1093/ornithology/ukae063)

Cañas-Valle, G.X. and J.L. Bouzat. 2024. Ecological drivers of coloniality in the Chimborazo Hillstar, Oreotrochilus chimborazo chimborazo, a hummingbird endemic to the High Andes of Ecuador. Ornithology 142(2): 1-13.