DOI: 10.5061/dryad.q83bk3jpb
title: Stable isotope composition of feathers and foraging behavior parallel bill shape divergence of Island Scrub-Jays (Aphelocoma insularis) in pine and oak habitats

description: Individual differences within populations have important ecological and
 evolutionary implications for understanding population-level responses to
 environmental variation. We found evidence of habitat-linked differences
 in stable isotopic composition of feathers and foraging behavior of Island
 Scrub-Jays (Aphelocoma insularis), endemic to Santa Cruz Island,
 California, USA, which parallel phenotypic divergence in jay bill shape
 between pine and oak habitats. We used stable isotopes of hydrogen (δD),
 carbon (δ13C), and nitrogen (δ15N) from feathers and direct observations
 of foraging behavior to infer habitat-specific diet variation among Island
 Scrub-Jays. Although hydrogen isotope composition of feathers did not
 differ between habitats as we expected, jays sampled in pine habitat were
 more enriched in 13C, whereas jays sampled in oak habitat were more
 enriched in 15N. Foraging observations indicated that diets largely
 overlapped in the 2 habitats, but jays in pine were more likely to consume
 arthropods. Jays in pine habitat also used relatively more probing,
 sallying, and pecking foraging maneuvers to capture prey. These findings
 suggest new avenues of research for understanding how habitat-linked,
 phenotypic divergence shapes behavior and diet of the omnivorous Island
 Scrub-Jay.
description: # Stable isotope composition of feathers and foraging behavior parallel
 bill shape divergence of Island Scrub-Jays (Aphelocoma insularis) in pine
 and oak habitats Dataset DOI:
 [10.5061/dryad.q83bk3jpb](10.5061/dryad.q83bk3jpb) ## Description of the
 data and file structure **Foraging data:** Opportunistically collected
 foraging data between September to November 2009-2012 from Island
 Scrub-Jays on Santa Cruz Island. For focal observations, observers waited
 for 5 min for an individual to acclimate to their presence before
 observing foraging through binoculars and recording details into digital
 voice recorders. We recorded the following details: food item taken
 (insect, acorn, fruit, seed), whether the individual was successful at
 taking the food item (consuming, carrying away), and foraging maneuver.
 **Stable isotope data**:  Measured δD, δ15N, and δ13C in breast feathers
 collected from 50 adult (&gt;1-year-old) Island Scrub-Jays between 2009
 and 2011. Analyses were conducted at the Smithsonian Stable Isotope Mass
 Spectrometry Laboratory in Suitland, Maryland, in September 2011–April
 2012.  ### Files and variables #### File: ISSJ_Foraging.Rmd
 **Description:** R code to run all analyses #### #### File:
 foraging_data_all_clean.csv **Description:**  Opportunistically collected
 foraging data between September to November 2009-2012 from Island
 Scrub-Jays on Santa Cruz Island. For focal observations, observers waited
 for 5 min for an individual to acclimate to their presence before
 observing foraging through binoculars and recording details into digital
 voice recorders. We recorded the following details: food item taken
 (insect, acorn, fruit, seed), whether the individual was successful at
 taking the food item (consuming, carrying away), and foraging maneuver.
 ##### Variables * color_ban_lr: The banding scheme is such that birds are
 banded with an aluminum band on their right leg with two color bands
 beneath the aluminum, one denoting the location on the island in which it
 was banded and the other denoting its cohort.  The left leg of each bird
 has been banded with a unique combination of three color bands. The only
 exception to this rule is at the Field Station, where the older birds were
 banded by Charlie Collins and have two bands on each leg.  In contrast to
 the adults, birds banded as nestlings prior to 2013 have an aluminum band
 on their left leg (or legs get mixed up during banding), with a color band
 on the same leg corresponding to the plot where they hatched. If the birds
 were recaptured then three color bands were added to their right leg. This
 banding scheme was designed to facilitate the identification of birds
 banded as nestlings and, in particular, to make every effort to pay
 special attention to and track down birds that have a color band
 indicating that they were banded on a different part of the island. The
 band abbreviations are as follows: A = aluminum                          
       P = purple R = red                                                  
   K = pink G = green                                                B =
 black O = orange                                              U = blue W =
 white * sex: male = M, female= F, U= unknown * plot: refers to the study
 plot the birds was sampled from.   o   PZ- Portezuela  o   FS- Field
 Station  o   CPC- Coches Prietos   o   CEN- Centinela (same as Buena
 Vista, “BV”, in Figure 1) o   Christy- pines west of Centinela o   SZ
 Off-Plot – anywhere not on one of the listed plots o   SZ IS - Isthmus
 (Navy site in Figure 1) o   Pelican- pines North of Field Station *
 habitat: Plots (see above) are classified as “pine” or “oak”, based on
 prior studies (Langin et al. 2015; Cladwell et al. 2013). Pine = Christy,
 CEN, Pelican; Oak= CPC, FS, PZ, IS * date: date the observation was made
 (month/day/year) * year: year observation was made *
 focal_observation: (yes, no) observation was collected for 30 minute
 focal. * substraight: Substrate (ground, air [AERO], plant species or
 type) | Veg Codes | Common name | Latin name | | :-------- |
 :--------------------- | :--------------------------- | | 
 
 | 
 
 | 
 
 | | ADFA | Chamise | Adenostoma Fasciculatum | | ARCA | Sagebrish  |
 Artemesia californica | | ARDO | Mugwort | Artemesia douglasiana | | ARSP
 | Manzanita  | Arctostaphylos spp. | | BAPL | Plummers Baccharis |
 Baccharis plummerae | | BAPI | Coyote brush | Baccharis pilularis | | BASA
 | Mulefat | Baccharis salicifolia | | CEAR | California lilac | Ceanothus
 arboreus | | CEME | Bigpod ceanothus | Ceanothus megacarpus | | CETR |
 Mountain mahogany | Cercocarpus... | | CODI | Summer holly |
 Comarostaphylis diversifolia | | DEAD | Dead veg | 
 
 | | DEHA | Island bush poppy | Dendromecon harfordii | | DEPI | Dead Pine
 | 
 
 | | DEPID | Dead Pine Down | 
 
 | | DEPIU | Dead Pine Upright | 
 
 | | ERFA | Buckwheat | Eriogonum spp. | | FORB | Forbes of grass | Family
 Poaceae | | FOVU | Fennel | Foeniculum vulgare | | HADE | Island
 Bristleweed | Hazardia detonsa | | HEAR | Toyon | Heteromeles arbutifolia
 | | KECO | Climbing penstemmon | Keckiella cordifolia | | LAVE | Wild pea
 | Lathyrus vestitus | | LODE | Island deerweed | Lotus dendroideus | |
 LYFL | Ironwood | Lyonothamnus floribundus | | MALL | Mallow spp. | Family
 Malvaceae | | MARA | Wild cucumber | Marah spp. | | MIMU | Monkeyflower |
 Mimulus spp. | | NONE | No species | 
 
 | | PIMU | Bishop pine | Pinus muricata | | POFR | Cottonwood | Populus
 freemontii | | PRIL | Island Cherry | Prunus ilicifolia | | QUAG | Live
 oak | Quercus agrifolia | | QULO | Valley oak | Quercus lobata | | QUMA |
 MacDonald's oak | Quercus macdonaldii | | QUPA | Scrub oak | Quercus
 pacifica | | RHCR | Red berry | Rhamnus crocea | | RHIN | Lemonade berry |
 Rhus integrifolia | | RHOV | Sugar bush | Rhus Ovata | | RITH | SCI
 Gooseberry | Ribes thacherianum | | SALA | Arroyo willow | Salix
 lasiolepis | | SAME | Black sage | Salvia mellifera | | SNAG | Tree snag/
 upright log | 
 
 | | TODI | Poison oak | Toxicodendron diversilobum | | UNKN | Unknown
 plant | 
 
 | | VECA | Canyon Sunflower | Venegasia carpesioides | | COGI | Giant
 coreopsois | 
 
 | | SOCL | Island Nightshade | Solanum clokeyi | * substraight_material:
 substrate material (for ground: soil, grass, moss, rock, leaf-litter, etc;
 for plants: leaves, flowers, bark, fruit; for air: not applicable) *
 foraging_maneuver: Foraging maneuver (definitions from Remsen &
 Robinson 1990) o *Glean*: to pick food items from a nearby substrate,
 including the ground, that can be reached without full extension of legs
 or neck; no acrobatic movements are involved. o *Reach*: to extend
 completely the legs or neck upwards, outwards, or downwards to reach food.
 o *Hang*: to use legs and toes to suspend the body below the feet to reach
 food that cannot be reached from any other perched position. o *Lunge*:
 those maneuvers in which the food item is beyond the range of “reach,” but
 rapid leg movements rather than flight are used to approach and capture
 prey (e.g. on ground). o *Probe*: to insert the bill into cracks or holes
 in firm substrate or directly into softer substrate such as moss or mud to
 capture hidden food. o *Peck*: to drive the bill against the substrate to
 remove some of the exterior of the substrate. o *Flake*: to brush aside
 *loose* substrate with sideways, sweeping motions of the bill. o *Pry*: to
 insert the bill into a substrate and use it as a lever to lift up portions
 of substrate. o *Scratch*: to dislodge section of substrate with foot
 movements. o *Sally*: to fly from a perch to attack a food item (and then
 return to a perch) * food: NA if no food was obtained, UNK if observer
 could not tell. Observers identified prey species through binoculars and
 only recorded prey items if they could actually see the prey item *
 successful: (yes no) did the individual consume or carry away the food
 item * comment_1: note of any observations on individuals thought to be
 floaters, observations made during unfavorable weather, and anything else
 that was thought to be noteworthy * comment_2: note of any observations on
 individuals thought to be floaters, observations made during unfavorable
 weather, and anything else that was thought to be noteworthy #### File:
 ISSJ_IsotopeData_all.csv **Description:** Measured δD, δ15N, and δ13C in
 breast feathers collected from 50 adult (&gt;1-year-old) Island Scrub-Jays
 between 2009 and 2011. Analyses were conducted at the Smithsonian Stable
 Isotope Mass Spectrometry Laboratory in Suitland, Maryland, in September
 2011–April 2012. ##### Variables * aluminum_band: Unique numerical code
 associated with the United States Geological Survey bird banding program.
 * tissue_number: The acquisition number given to each unique tissue. *
 date_banded: the data the individuals was banded and sampled * Year: the
 year the individual was sampled * age: Age at the banding record  is
 denoted as : N (Nestling),  HY (Hatch Year), SY (Second Year), or AHY/ASY
 (After Hatch Year/After Second Year). * Sex: male = M, female= F, U=
 unknown * Mates_band: The USGS aluminum band combination for the
 individua;s mate (if from a mated pair). * dD: Relative abundance of
 deuterium (H2) in the sample * d15N: Relative abundance of N15 in the
 sample * d13C: Relative abundance of C13 in the sampl * d34S: Relative
 abundance of S34 in the sample * location:  refers to the study plot the
 birds was sampled from.   * PZ- Portezuela  * FS- Field Station  * CPC-
 Coches Prietos   * CEN- Centinela (same as Buena Vista, “BV”, in Figure 1)
 * Christy- pines west of Centinela * SZ Off-Plot – anywhere not on one of
 the listed plots * SZ IS - Isthmus (Navy site in Figure 1) * Pelican-
 pines North of Field Station * habitat: Plots (see above) are classified
 as “pine” or “oak”, based on prior studies (Langin et al. 2015; Cladwell
 et al. 2013). Pine = Christy, CEN, Pelican; Oak= CPC, FS, PZ, IS * plot:
 (see location) * longitude: the longitude where an individual was captured
 and sampled * latitude: the latitude where an individual was captured and
 sampled * percent_pine: The  proportion of pine vegetation within
 300-meters of an individual's sampling location. * percent_oak: The
 proportion of oak vegetation within 300-meters of an individual's
 sampling location * percent_other: The proportion of “other” (e.g.
 grasslands, bare ground, scrub) vegetation within 300-meters of an
 individual's sampling location ## Code/software R code to run all
 analyses included in the ISSJ_Foraging.Rmd