DRAFT ENVIRONMENTAL ASSESSMENT for RESTORATION OF HABITAT ON THE DESECHEO NATIONAL WILDLIFE REFUGE THROUGH THE ERADICATION OF NON- NATIVE RATS Desecheo, Puerto Rico Lead Agency: U.S. Fish and Wildlife Service P.O. Box 510 Boqueron, Puerto Rico 00622 December 2015 Table of Contents Introduction ....................................................................................................................................1 1.0 Purpose of and Need for Action ...........................................................................................1 1.1 Purpose of Action .............................................................................................................1 1.2 Need(s) for action .............................................................................................................1 1.3 Summary of previous eradication attempt ........................................................................3 1.4 Decision(s) to be Made .....................................................................................................3 1.5 Scoping Process ................................................................................................................4 1.6 Issues and Concerns ..........................................................................................................4 2.0 Alternatives ............................................................................................................................5 2.1 Alternative A- No Action Alternative ...............................................................................5 2.2 Action alternatives: Common Features .............................................................................6 2.2.1 Rodent bait ...............................................................................................................6 2.2.2 A Comparison of Two Bait Products Registered for Conservation Purposes: Brodifacoum-25D (Alternative B) and Diphacinone-50 (Alternative C) ................6 2.2.2.1 Introduction ..................................................................................................6 2.2.2.2 Brodifacoum and Brodifacoum-25D bait product .......................................8 2.2.2.3 Diphacinone and Diphacinone-50 bait product ...........................................9 2.2.3 Comparative Likelihood of Success ......................................................................11 2.2.4 Bait Trials Conducted on Desecheo Island ............................................................14 2.2.4.1 Rat Eradication Feasibility Study, February 2009 .....................................14 2.2.4.2 Bait Uptake Trials and Bait Availability ...................................................15 2.2.4.3 Bait Degradation .......................................................................................17 2.2.5 Aerial Broadcast.....................................................................................................18 2.2.6 Timing Considerations ...........................................................................................18 2.2.7 Biology of Rats & Timing of Eradication Operation .............................................19 2.2.8 Seasonal Patterns of Native Wildlife .....................................................................19 2.2.8.1 Weather Considerations .............................................................................20 2.2.9 Project Staging and Support Operations ................................................................20 2.2.10 Reducing Wildlife Disturbance during Operations..............................................21 2.2.11 Protecting Cultural Resources ..............................................................................21 2.2.12 Monitoring Eradication Efficacy .........................................................................21 2.2.13 Monitoring Ecosystem Response .........................................................................22 2.2.14 Public Information ...............................................................................................22 2.2.15 Re-introduction Prevention ..................................................................................23 2.3 Alternative B: Aerial Broadcast as Primary Delivery Technique of Brodifacoum-25D Bait Product ....................................................................................................................23 2.3.1 Rationale ................................................................................................................23 2.3.2 Difference between Alternative B and Brodifacoum 25D Alternative of 2012 ....23 2.3.3 Summary of Bait Delivery Methods ......................................................................24 2.3.4 Timing ....................................................................................................................24 2.3.5 Equipment and Materials .......................................................................................24 2.3.5.1 Aerial Broadcast Equipment ......................................................................24 2.3.5.2 Bait Stations ...............................................................................................25 2.3.6 Bait Application Operations ..................................................................................25 2.3.6.1 Aerial Broadcast.........................................................................................25 2.3.7 Preventing Bait Spread into the Marine Environment ...........................................26 2.3.8 Coverage of Baiting Gaps ......................................................................................26 2.4 Alternative C: Aerial Broadcast as Primary Delivery Technique of Diphacinone-50 Bait Product ............................................................................................................................27 2.4.1 Rationale ................................................................................................................27 2.4.2 Summary of Bait Delivery Methods ......................................................................27 2.4.3 Timing ....................................................................................................................28 2.4.4 Equipment and Materials .......................................................................................28 2.4.4.1 Bait .............................................................................................................28 2.4.4.2 Aerial Broadcast Equipment ......................................................................28 2.4.4.3 Bait Stations ...............................................................................................28 2.4.5 Bait Application Operations ..................................................................................28 2.4.5.1 Aerial Broadcast.........................................................................................29 2.4.6 Preventing Bait Spread into the Marine Environment ...........................................30 2.4.7 Coverage of Baiting Gaps ......................................................................................30 2.5 Alternatives Dismissed from Detailed Analysis .............................................................30 3.0 Affected Environment ........................................................................................................30 3.1 General Description of Desecheo ...................................................................................30 3.1.1 Geographical Setting…………………………………………………………….30 3.1.2 Topography ............................................................................................................31 3.1.3 Climate ...................................................................................................................31 3.2 Physical Resources..........................................................................................................33 3.2.1 Water Resources ....................................................................................................33 3.2.2 Geology and Soils ..................................................................................................33 3.2.3 Air Quality .............................................................................................................33 3.3 Biological Resources ......................................................................................................33 3.3.1 Birds on Desecheo .................................................................................................34 3.3.1.1 Historical and Current Status .....................................................................34 3.3.1.2 Species Records .........................................................................................35 3.3.1.3 Avian Seasonal Patterns .............................................................................36 3.3.1.4 Landbirds and Waterbirds ..........................................................................37 3.3.1.5 Seabirds ......................................................................................................37 3.4 Special Legal Protection for Birds on Desecheo ............................................................39 3.4.1 Endangered Species Act ........................................................................................39 3.4.2 Migratory Bird treaty Act ......................................................................................39