Phenology

Quantifying phenological landmarks of migration shows nonuniform use of the Caribbean by shorebirds

Abstract

Of   the   boreal-  and   Arctic-    breeding North     American shorebirds that   migrate south through the   Caribbean, most    individuals continue farther south.     However, for   many species, some    individuals remain beyond the   southbound migration period (i.e., throughout the   temperate winter and/or summer). This   variation among individuals adds   complexity to  observation data,    obscures migration patterns, and   could    preventthe   examination of  the   use   of  different Caribbean regions by  various shorebird species during     migration and   in  the   nonmigratory seasons. Here,    we   present a  novel    method that   leverages a  well-   established statistical approach (generalized additive models) to systematically identify migration phenology even    for   complex passage migrant spe -cies   with    individuals that   remain beyond migration. Our   method identifies the   active migration period    using    derivatives of  a  fitted    GAM   and   then   calculates phenology metrics   based    on  quantiles of  that   migration period. We   also   developed indices to  quantify oversummering and   overwintering patterns with    respect to  migration. We   analyzed eBird    data    for   16  North    American shorebird species as  they    traveled South    through the   insular Caribbean, identifying separate migratory patterns for   Cuba,    Puerto Rico, Guadeloupe, Aruba, Bonaire, Curaçao, and   Trinidad and   Tobago. Our   results confirm past   reports and   provide additional detail    on   shorebird migration in  the   Caribbean, and   identify several previously unpublished regional patterns. Despite Puerto Rico being    farther north    and   closer    to  continental North    America, most  species reached Puerto Rico   later    than    other    regions, supporting a  long-   standing hypothesis that   mi -gration strategy (transcontinental vs.   transoceanic) leads    to  geographic differences in  migration timing. We   also   found  distinct patterns of  migration curves, with    some regions and   species consistently having either    symmetrical or  skewed curves; these differences in  migration curve    shape    reflect     different migration processes. Our   novel  method proved reliable and   adaptable for   most    species and   serves     as  a  valuable tool for   identifying phenological patterns in  complex migration data,    potentially unlocking previously intractable data.

Date
2023
Data type
Scientific article
Theme
Research and monitoring
Geographic location
Aruba
Bonaire
Curacao

The reproductive phenology of three sympatric species of columnar cacti on Curacao

The phenological response by three sympatric species of columnar cacti of the semi-arid island of Curaçao (Stenocereus griseus, Subpilocereus repandus, and Pilosocereus lanuginosus) to recent rainfall was investigated during 21 months. Rainfall is the climatic cue most likely to affect bud formation on Curaçao, and each species of cactus responded differently to it. Pilosocereus lanuginosus started budding immediately after rainfall, whereas Stenocereus griseus responded negatively with abortions and cessation of bud production within 2–3 weeks after rain. Subpilocereus repandus showed no response to rain within one month. Despite a long period of temporal overlap (81% overlap) between the budding/flowering activity of Subpilocereus repandus and that of Stenocereus griseus, buds and/or flowers on Stenocereus griseus appeared more than a month earlier than on Subpilocereus repandus.
The effect of plant size on phenology and how anthropogenic disturbance may affect cactus resource availability to nectar-feeders and frugivores were also examined. The larger the individual tree within a species, the more flowers were produced and the earlier the tree started to flower. Thus, the indiscriminate removal of columnar cacti for urban development can drastically affect the timing and availability of resources to threatened pollinators and other nectar-feeders, as well as to frugivores and omnivores.

Date
2001
Data type
Scientific article
Theme
Research and monitoring
Geographic location
Curacao
Author