Factors influencing mortality in a captive breeding population of Loggerhead Shrike, Eastern subspecies (Lanius ludovicianus ssp.) in Canada
Bibliographic record
Abstract
BACKGROUND: The Loggerhead Shrike, Eastern subspecies (Lanius ludovicianus ssp.) (LOSH) is a predatory songbird native to Eastern North America. It is estimated that there are fewer than 55 breeding pairs of this subspecies in North America. Captive breeding plays a critical role in preventing the extirpation of this subspecies from its Canadian range. Unfortunately, high numbers of unexplained deaths among young birds in the captive breeding population threatened the success of this program. This paper describes fledgling mortality in the captive breeding population, and seeks to identify factors associated with fledgling survival and, ultimately, to identify steps to mitigate fledgling mortality. RESULTS: Over the study period (2006-2011) at two breeding sites, 696 LOSH were fledged. Among these, 68 % (n = 474) were released, 10 % (n = 69) were retained in the captive breeding population, and 22 % (n = 155) died. Fledgling survival declined from 99 % in 2006 to 44 % in 2011. The odds of survival were significantly lower for fledglings that were part of a second clutch. As the number of fledglings in a clutch increased, the odds of surviving increased significantly. As the breeding female aged from one to four years of age, there was a marked increase in the odds of a fledgling surviving, which then subsequently declined as females aged further. CONCLUSIONS: Based on our analyses, clutch number (first or second), number of fledglings in the brood, and age of breeding females were significant predictors of fledgling survival. Long-term breeding management decisions will have to balance the need to increase the number of individuals and breeding pairs in the wild by releasing large numbers of young, against the need to maintain a genetically viable captive population, until the wild population is large enough to be self-sustaining.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".