Seasonal Changes in Brain GnRH Immunoreactivity and Song-Control Nuclei Volumes in an Opportunistically Breeding Songbird
Bibliographic record
Abstract
White-winged crossbills (Loxia leucoptera) are opportunistic breeders that can nest at almost any time of year if there is sufficient food. Other cardueline finches that have been shown to breed on a strictly seasonal schedule become absolutely refractory to the stimulatory effects of long-day photoperiod, dramatically down-regulate hypothalamic gonadotropin-releasing hormone (GnRH), and reduce the volume of several song-control nuclei in autumn. This study examined whether changes in photoperiod modify the GnRH and song-control systems in white-winged crossbills. Adult male and female crossbills were captured and held on a naturally changing photoperiod. Brains of male and female birds were collected in May, October, and January. GnRH content was assessed by immunocytochemistry and the volumes of Nissl-defined song-control nuclei (HVc, Area X, and the robust nucleus of the archistriatum) were reconstructed. In contrast to other cardueline finches, GnRH immunoreactivity was relatively stable across the year, exhibiting only modest seasonal variation. The song control system, on the other hand, exhibited large seasonal changes as well as sex differences. Thus, crossbills appear to maintain hypothalamic GnRH content year round, perhaps to facilitate a rapid response to favorable breeding conditions, even on short days. However, song control nuclei are dramatically affected by photoperiod. Future work should examine these systems in crossbills breeding on short days to compare photoperiod-dependent and -independent effects on neural plasticity.
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 machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 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) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".