Point-count bird censusing: long-term monitoring of bird abundance and diversity in central Arizona-Phoenix, ongoing since 2000

project overview Over the past half-century, the greater Phoenix metropolitan area (GPMA) has been one
of the fastest growing regions in the US, experiencing rapid urban expansion in addition
to urban intensification. This backdrop provides an ideal setting to monitor biodiversity
changes in response to urbanization, and the CAP LTER has been using a standardized
point-count protocol to monitor the bird community in the GPMA and surrounding Sonoran
desert region since 2000. The bird survey locations in this CAP LTER core monitoring program include six
general site groupings: ESCA. Forty bird survey locations were selected from a subset of the CAP LTER's
Ecological Survey of Central Arizona (ESCA; formerly named Survey200) long-term
monitoring sites. ESCA sites were located using a tessellation-stratified
dual-density sampling design, and, as such, span a diversity of habitats including
urban, suburban, rural, commercial areas, parks, agricultural fields, and native
Sonoran desert. Earlier versions of this data package included data from the ESCA
project that was intended to complement the bird data. However, while positioned in
close proximity, the bird survey locations do not necessarily overlap with the 30m x
30m plot that constitutes an ESCA sampling location, and leveraging data from these
two monitoring programs should be addressed carefully. ESCA data have corresponding
survey location names, and those data are available through the CAP LTER and LTER
network data portals. At the conclusion of the 2016 spring survey, fifteen of the
ESCA-correlated sites were discontinued as the core monitoring program refocused its
efforts on desert parks and PASS neighborhoods. Among the deleted locations were all
agricultural and commercial sites, as well as sites where access had become
restrictive. North Desert Village (NDV). Additional bird survey locations were positioned in
treatment areas of the North Desert Village (NDV). This was a site of intense study
on the Arizona State University Polytechnic Campus in which the CAP LTER converted
the landscaping of small neighborhoods to reflect the dominant landscaping
preferences employed throughout the GPMA. NDV landscape types include: oasis
(NDV-O), xeric (NDV-X), mesic (NDV-M), control (NDV-C), and native (NDV-N).
Monitoring at NDV was discontinued after the spring 2016 season as research efforts
at this site came to an end. Riparian. While the forty bird survey locations that were selected to coincide
with ESCA sampling locations span a wide diversity of habitats throughout the GPMA,
because of the generally random nature of selecting those sites, they did not
reflect riparian habitats. Riparian areas are important bird habitat but constitute
a very small area of the GPMA. To address this deficiency, bird survey locations
were established specifically in twelve riparian habitats. Riparian habitat
sub-types include: (1) ephemeral-engineered (EE, n=4), (2) ephemeral-natural (EN,
n=2), (3) perennial-engineered (PE, n=3), and (4) perennial-natural (PN, n=3). This
research was successfully concluded and these sites were discontinued after the
spring 2016 season. Salt River. Seven study sites along the Salt River as it runs through the GPMA
that were selected as part of a related study (Salt River Biodiversity Project
(SRBP)) were ultimately included in the CAP LTER's core bird monitoring programs.
These sites reflect continued monitoring of riparian habitat. Desert Fertilization. Beginning with the 2016-2017 winter survey, six sites at
desert parks were added to core monitoring to coincide with the CAP LTER Desert
Fertilization (DesFert) experiment sites. PASS. Beginning with the 2016-2017 winter survey, what used to be a separate
bird-monitoring effort (monitoring in Phoenix Area Social Survey (PASS)
neighborhoods) was incorporated into this core bird-monitoring program. Eight points
were carried over from prior PASS monitoring, and 28 new points established,
resulting in three bird monitoring locations in each of the twelve PASS
neighborhoods. Visiting these locations each year, versus only in years surrounding
the PASS survey as done previously, provides more data on bird populations found in
the neighborhoods of the CAP LTER study area. method overview In a given season, each bird survey location is visited independently by three
birders who count all birds seen or heard within a 15-minute window. The frequency of
surveys has varied through the life of the project. The first year of the project (2000)
was generally a pilot year in which each site was visited approximately twice by a varying
number of birders. The monitoring became more formalized beginning in 2001, and each site
was visited in each of four seasons by three birders. The frequency of visits was reduced
to three seasons in 2005, and to two season (spring, winter) beginning in 2006.

项目概况
过去半个世纪以来，大凤凰城都会区（Greater Phoenix Metropolitan Area, GPMA）一直是美国增长最快的区域之一，不仅经历了快速的城市扩张，同时也伴随着城市集约化发展。这一背景为监测城市化进程下的生物多样性变化提供了理想的研究场景。自2000年起，CAP长期生态研究站（CAP LTER）便采用标准化点计数监测方案，对大凤凰城都会区及周边索诺兰沙漠区域的鸟类群落开展长期监测。
本CAP LTER核心监测项目的鸟类调查点位共分为六大类群组：
ESCA：从CAP LTER的亚利桑那州中部生态调查（Ecological Survey of Central Arizona, ESCA，前身为Survey200）长期监测点位中，选取了40个鸟类调查点位。ESCA点位采用镶嵌分层双密度采样设计布设，涵盖城市、郊区、乡村、商业区、公园、农田及原生索诺兰沙漠等多样生境。早期版本的数据包中包含了用于辅助鸟类调查数据的ESCA项目数据，但尽管二者点位位置相近，鸟类调查点位未必与ESCA采样所用的30米×30米样地重合，因此整合这两个监测项目的数据时需谨慎处理。ESCA数据带有对应的调查点位名称，可通过CAP LTER及LTER网络数据门户获取。2016年春季调查结束后，由于核心监测项目将工作重心调整至沙漠公园与PASS社区，15个与ESCA关联的点位被停用，其中包含全部农业与商业点位，以及难以进入的点位。
北沙漠村落（North Desert Village, NDV）：在北沙漠村落的处理样区增设了鸟类调查点位。该点位位于亚利桑那州立大学理工学院校区内，是CAP LTER的重点研究场地，旨在将小型社区的景观改造为贴合大凤凰城都会区主流景观偏好的样式。NDV的景观类型包括：绿洲型（NDV-O）、旱生型（NDV-X）、湿生型（NDV-M）、对照型（NDV-C）及原生型（NDV-N）。2016年春季调查结束后，该场地的研究工作终止，NDV的监测也随之停止。
河岸生境：此前选取的与ESCA采样点位匹配的40个鸟类调查点位虽覆盖了大凤凰城都会区多样生境，但由于点位选取整体偏向随机，未涵盖河岸生境。河岸区域是重要的鸟类栖息生境，但在大凤凰城都会区内占比极低。为弥补这一缺陷，项目组专门在12处河岸生境中设立了鸟类调查点位。河岸生境亚型分为：(1) 季节性人工修复型（ephemeral-engineered, EE, n=4）、(2) 季节性自然型（ephemeral-natural, EN, n=2）、(3) 常年人工修复型（perennial-engineered, PE, n=3）、(4) 常年自然型（perennial-natural, PN, n=3）。该研究已于2016年春季调查结束后顺利完成，相关点位随之停用。
盐河（Salt River）：作为相关研究「盐河生物多样性项目（Salt River Biodiversity Project, SRBP）」的一部分，沿流经大凤凰城都会区的盐河选取的7个研究点位，最终被纳入CAP LTER的核心鸟类监测项目，用于持续监测河岸生境。
沙漠施肥实验（Desert Fertilization）：自2016-2017年冬季调查起，项目组在沙漠公园增设了6个监测点位，与CAP LTER的沙漠施肥实验（Desert Fertilization, DesFert）样地相匹配。
凤凰城区域社会调查社区（Phoenix Area Social Survey, PASS）：自2016-2017年冬季调查起，原本独立开展的鸟类监测工作——即对PASS社区的鸟类监测——被纳入本核心鸟类监测项目。项目保留了此前PASS监测中的8个点位，并新增28个点位，最终在12个PASS社区各设立3个鸟类监测点位。与此前仅在PASS调查年份前后开展监测不同，如今每年都会对这些点位进行调查，从而获取CAP LTER研究区域内社区鸟类种群的更多数据。

方法概述
在每个调查季，3名鸟类观察员会独立到访每个鸟类调查点位，在15分钟的观测窗口内记录所见或所闻的全部鸟类。项目开展期间，调查频次经历了多次调整：项目首年（2000年）整体为试点阶段，每个点位由不同数量的鸟类观察员到访约2次；2001年起监测工作趋于规范化，每个点位每年在4个季节各由3名观察员到访1次；2005年调查频次缩减为每年3个季节，2006年起进一步调整为每年2个季节（春季与冬季）。